Hardware controlled transfers to microprogram control apparatus and return via microinstruction restart codes

ABSTRACT

A microprogrammed pipeline data processing unit includes a first control store, a second control store and a plurality of hardware sequence control circuits. The first control store includes a plurality of storage locations, each location for storing an address field and a control sequence field for each program instruction required to be executed by the processing unit. The second control store includes a plurality of groups of storage locations, each group storing microinstructions required for executing at least a portion of at least one program instruction. Each sequence includes at least one microinstruction which contains a restart field coded to specify the conditions under which the hardware sequence circuits continue instruction execution. For each program instruction which can not be executed by the plurality of hardware sequence circuits in a pipeline mode, the control sequence field is coded to include a predetermined bit pattern. When decoded, the hardware sequence circuits is conditioned to enter an escape state enabling control to be transferred to a sequence specified by the address field. Instruction execution proceeds under microprogram control while the hardware sequence circuits remain in the same state. Upon the decoding of a microinstruction containing a restart field, the hardware sequence circuits are switched from the escape state to a state which enables the continuing of hardware instruction execution in a pipeline mode.

RELATED APPLICATIONS

1. "Data Processing System Programmable Pre-Read Capability" invented by John E. Wilhite, William A. Shelly and Charles P. Ryan, Ser. No. 853,944, filed on Nov. 22, 1977 and assigned to the same assignee as named herein.

2. "A Microprogrammed Computer Control Unit Capable of Efficiently Executing a Large Repertoire of Instructions for a High Performance Data Processing Unit" invented by John E. Wilhite, Ser. No. 853,946, filed on Nov. 22, 1977 and assigned to the same assignee as named herein.

BACKGROUND OF THE INVENTION

1. Field of Use

The present invention relates to data processing systems and more particularly to microprogrammed data processing systems.

2. Prior Art

In general, in order to reduce the storage requirements of a microprogrammed control element, some systems have employed two control stores. Such a system is disclosed in U.S. Pat. No. 4,001,788 which is assigned to the assignee of the present invention.

While such arrangements have considerable advantages, it is noted that the overall performance of such microprogrammed data processing units are less due to the time required to be expended in decoding a series of microinstructions for execution of a program instruction.

Another system includes a microprogrammed control unit which includes a control store and a hardware sequencer network for generating additional microoperation commands at higher speeds in response to address or control signals from such store together with condition signals. This system is disclosed in U.S. Pat. No. 3,872,447. An enabling signal or a microinstruction from a control store is used to effect the operation of the hardware sequencer network.

While the above arrangement increases system speed, it essentially operates to extend the number of microcommands which may be obtained from a microinstruction without requiring an extension of the length of the microinstruction. However, such additional microcommands are arranged to be dependent upon the addresses of the microinstruction and condition signals.

Hence, execution of program instructions primarily proceeds under microprogram control whereby the overall performance of the system is still substantially less than hardwired data processing system.

The performance of a microprogrammed control unit becomes even more important in the case of high performance pipe-lined processing systems. Such systems typically perform instructions which are stored in a high speed low capacity buffer or cache unit in such a manner that more than one instruction is actually being processed at any one instant of time. Since instructions can be fetched faster from memory, this results in such increased performance.

To retain the efficiency of such systems, it has been the practice to utilize non microprogrammed control units. The reason is that even those microprogrammed control units include apparatus which increases operating speed, such units are not well suited for efficiently controlling a pipeline data processing unit. However, it has been found that such non microprogrammed control units are more complex and require hardware circuit changes for changes in instructions.

Accordingly, it is a primary object of the present invention to provide a high performance microprogrammed control unit.

It is a further object of the present invention to provide a microprogrammed control unit for use in a pipeline data processing unit.

SUMMARY OF THE INVENTION

The above objects and advantages of the present invention are achieved in a preferred embodiment of a microprogrammed pipelined data processing unit. The unit includes a first control store, a second store, decoder circuits and a plurality of hardware sequence control circuits. The first control store includes a plurality of storage locations, each location for storing an address field and an address field and a control sequence field for each program instruction required to be executed by the processing unit.

The second control store includes a plurality of groups of storage locations, each group storing microinstructions executing at least a portion of at least one program instruction. Each microinstruction sequence includes at least one microinstruction which contains a restart field coded to specify the conditions under which the hardware sequence control circuits restart the pipeline operation to continue instruction execution.

In accordance with the teachings of the present invention, for each program instruction which cannot be executed during pipeline operation, the control sequence field of the location referenced by the instruction is coded to include a predetermined bit pattern. Decoder circuits are operative upon decoding such pattern to condition the hardware control sequence circuits to switch to a predetermined state termed an escape state. When in this state, the hardware control sequence circuits transfer control to the microinstruction sequence specified by the address field of the referenced location.

Execution of the program instruction thereafter proceeds under microprogram control while the hardware sequence circuits remain in the escape state. Upon the read out of a microinstruction containing a restart field, decoding circuits are operative to switch the hardware control sequence circuits from the escape state to a state for restarting pipeline operation to continue instruction execution.

In accordance with the preferred embodiment, the restart field is coded to specify the type of restart conditions. For example, a first coded bit pattern of the restart field causes a restart of pipeline operation resuming instruction processing beginning with the next instruction following transfer or release of control to the hardware control sequence circuits.

The above type of restart is utilized for those types of instructions where it is possible to estimate when execution of such instructions will be completed. In such cases, a microinstruction located at a predetermined point within the sequence of microinstructions specified to execute such as instructions is coded to include a restart field coded to specify this first coded bit pattern. The point is selected so as to provide a continuity of instruction execution cycles. In the preferred embodiment, a point is selected at which the microinstruction read out signals restart of time approximating the interval of time required for an instruction to pass through the different stages of pipeline processing. For example, if the pipeline stages of instruction processing and a cache processing require a time interval of 2T, the restart field is included in a microinstruction which is executed at a point 2T prior to the completion of the execution phase of that instruction. Hence, there will be no idle cycles or breaks in the pipeline operation.

In accordance with the teachings of the present invention, second and third coded bit patterns of the restart field causes a restart of pipeline operation resuming instruction processing of the same or current instruction at a particular point established by the placing of the hardware control sequence circuits in a particular state following the release or transfer of the control thereto.

The above type of restarts are utilized for those types of instructions which specify certain types of operations which cannot be efficiently processed during pipeline operation and which specify additional operations which the hardware control sequence circuits are expeditiously process. For example, such instructions include those having multiple address or descriptor portions wherein one of the addresses specifies an indirect operand address requiring additional address development operations.

In accordance with the present invention, for each such instruction, the hardware sequence control circuits following completion of a portion of such instruction enter the escape state. Thereafter, the additional operation is executed under microprogram control through the sequence of microinstructions specified by the address stored in the first control store. Included within a referenced microinstruction sequence is a microinstruction coded to include a restart field specifying second or third coded bit patterns. Following execution of the microinstruction sequence, microprogram control is released and processing of the same instruction is continued under the control of the hardware sequence control circuits.

A fourth coded bit pattern of the restart field causes a restart to occur when the hardware control sequence circuits have been placed in a predetermined state when certain types of program instructions are being executed. In the preferred embodiment, the processing unit's instruction buffer is reloaded with instructions specified by the contents of the processing unit's instruction counter and processing begins with a first instruction within the buffer. The microinstruction coded to include this type of restart appears in the sequence of microinstructions following microinstructions specifying the loading of the instruction counter address.

Other coded bit patterns of restart fields enable a restart of pipeline operation signaled by the restart field included within a first microinstruction of a microinstruction sequence to occur before execution of the instruction has been completed under microprogram control. This causes the hardware sequence control circuits to execute an instruction cycle then a cache cycle of operation followed by an awaiting of further operations until receipt of a release specified by the restart field included a second subsequent microinstruction within the microinstruction sequence. This enables certain types of program instructions such as floating point arithmetic and shift instructions to be processed more efficiently.

From the foregoing, it is seen that the preferred embodiment enables selective transfers of control from hardware circuits to microprogram control during the pipelined processing of program instructions and restarting of such pipelined operation. In accordance with the teachings of the present invention, a number of different restarts can be specified under microprogram control thereby ensuring processing efficiency in the cases of a variety of different types of program instructions having different formats and different requirements.

Hence, the arrangement of the present invention ensures considerable flexibility in the types of instructions which can be processed. Also, it facilitates and simplifies the microprogramming of such program instructions as well as new program instructions when required to be added to the instruction repertoire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in block form a system employing the principles of the present invention.

FIG. 2 shows in block diagram form the host processor 700 and the cache memory 750 of FIG. 1.

FIGS. 3a through 3i show in greater detail the different blocks of FIG. 2.

FIG. 4 shows in greater detail the cache unit 750 of FIG. 2.

FIGS. 5a through 5e show the lines which comprise different ones of the interfaces of FIG. 1.

FIG. 6a illustrates the format of the control store control unit of FIG. 2 in accordance with the teachings of the present invention.

FIG. 6b illustrates the format of the microinstruction words of the execution control store of FIGS. 2 and 3.

FIG. 7 is a state diagram used in describing the hardware sequencing of the apparatus of the present invention.

FIG. 8 is a diagram used in explaining the pipeline operations of the processor 700 in processing different series of instructions in accordance with the present invention.

FIGS. 9a through 9d illustrate the formats of certain types of instructions used in describing the operation of the present invention.

FIGS. 10a through 10e illustrate the start pipeline operations in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT General Description

As seen from FIG. 1, the system which incorporates the principles of the present invention includes at least 1 input/output processor (IOPP) 200, a system interface unit (SIU) 100, a high-speed multiplexer (HSMX) 300, a low-speed multiplexer (LSMX) 400, a host processor 700, a cache memory 750, at least one memory module corresponding to a local memory module 500, and at least one memory module corresponding to a remote memory module 800. Different ones of these modules connect to one of a number of ports of the system interface unit 100 through a plurality of lines of different types of interfaces 600 through 603. More specifically, the input/output processor 200, the cache memory 750, and the high-speed multiplexer 300 connect to ports G, E and A, respectively, while the low-speed multiplexer 400, local memory module 500, and main memory module 800 connect to ports J, LMO and RMO, respectively. The host processor 700 connects to the cache memory 750.

The input/output system of FIG. 1 can be viewed as including a number of "active modules", "passive modules" and "memory modules". The IOP processor 200, host processor 700 and high-speed multiplexer 300 serve as active modules in that each has the ability to issue commands. The active modules normally connect to ports A through H while the host processor 700 connects to port E through the cache unit 750 via interfaces 604 and 600. A plurality of passive modules are connected to three ports J, K and L. These modules correspond to the low-speed multiplexer 400 and the system interface unit 100 and are units capable of intercepting and executing commands applied to the lines of interface 601 as described herein. The last group of modules constitutes local memory modules, and main memory modules capable of executing two different types of commands applied to the lines of interface 603.

The input/output system of FIG. 1 normally functions as an input/output subsystem responsive to input/output instructions issued by the host processor 700. Ports E and F include interfaces for enabling connection of either multiplexer or processor modules of FIG. 1. These interfaces are described in greater detail herein.

For the purpose of the present invention, host processor 700 is conventional in design and may take the form of those units described in U.S. Pat. No. 3,413,613. In the preferred embodiment, the input/output processor 200 initiates and terminates channel programs required for the execution of input/output instructions, processes interrupt requests received from the system interface unit 100, and directly controls unit record peripheral devices coupled to low-speed multiplexer 400. The processor 200 connects to port G via the data interface 600 and interrupt interface 602.

The low-speed multiplexer 400, for the purposes of the present invention can be considered conventional in design, provides for attachment of low-speed peripheral devices via peripheral adapters, each of which couples to the lines of a device adapter interface (DAI). The interface and adapter may take the form of those units described in U.S. Pat. No. 3,742,457, which is assigned to the assignee of the present invention. The low-speed devices include card readers, card punches and printers. As seen from FIG. 1, the multiplexer 400 connects to port J via the programmable interface 601.

The high-speed multiplexer 300 directly controls transfers between the groups of disk devices and tape devices 309 through 312, which connect to different ones of the channel adapters 303 to 306. Each of the channel controller adapters 303 through 306 which can connect up to a maximum of 16 devices to a different one of the channel ports 0 through 3 via the interface lines of a channel adapter interface (CAI) 300-1. The high-speed multiplexer 300 connects to port A corresponding to a data interface 600, a programmable interface 601 and an interrupt interface 602.

For the purposes of the present invention, each of the channel controller adapters 302 through 305 may be considered in design and take the form of controller adapters described in the aforementioned U.S. Pat. No. 3,742,457.

SYSTEM INTERFACES

Before describing in detail the processor 700 and cache unit 750, constructed in accordance with principles of the present invention, each of the interfaces 600 through 604 discussed previously will now be described with reference to FIGS. 5a through 5e.

Referring first to FIG. 5a, it is seen that this figure discloses the lines which constitute the data interface 600 which is one of the interfaces which provides for exchange of information between an active module and the system interface unit 100. Exchange is accomplished by controlling the logical states of various signal lines in accordance with pre-established rules implemented through a sequence of signals termed a "dialog".

As seen from FIG. 5a, the interface includes an active output port request line (AOPR), a plurality of data to SIU lines (DTS OO-DTS 35, P0-P3), a plurality of steering data to SIU lines (SDTS O-6, P), an active request accepted line (ARA), an accept read data line (ARDA), a plurality of data from SIU bus lines (DFS OO-35, P0-P3), a plurality of multiport identifier from SIU lines (MIFS O-3, P), a double precision from SIU line (DPFS), and an accept status line (AST). The description of the interface lines are given in greater detail in the section to follow.

    ______________________________________                                                  DATA INTERFACE LINES                                                  Designation                                                                               Description                                                         ______________________________________                                         AOPR       The active output port request line is an                                      unidirectional line which extends from                                         each of the active modules to the SIU 100.                                     When set, this line signals the SIU that                                       the module requests a transfer path over                                       which commands or data are to be trans-                                        mitted.                                                             DTS 00-35, P0-P3                                                                          The data path lines are a four byte wide                                       unidirectional path (four to 10 bit bytes)                                     that extends between each of the active                                        modules and the SIU and are used for trans-                                    ferring commands or data from each active                                      module to the SIU 100.                                              SDTS 0-6, P                                                                               The steering data to SIU lines extend from                                     each active module to the SIU 100. These                                       lines are used to apply steering control                                       information to the SIU 100 when the line                                       AOPR is set. Steering control information                                      consists of seven bits and a parity bit                                        which are coded as follows:                                                  (a) The state of bit 0 indicates the type                                          of command applied to the DTS lines                                            (whether the command is a pro-                                                 grammable interface command or a                                               memory command).                                                           (b) Bits 1-4 are coded to indicate which                                           one of the modules is to receive and                                           interpret the memory command (commands                                         are interpreted only by memory modules                                         and programmable interface commands                                            shall be interpreted by all modules                                            except input/output processor 200).                                        (c) The state of bit 5 indicates whether                                           one or two words of the command in-                                            formation is to be transferred be-                                             tween the requesting active module                                             and the designated receiving module                                            (one word specifies a single precision                                         transfer and two words specifies a                                             double precision transfer).                                                (d) The state of bit 6 indicates the                                               direction of transfer between the                                              requesting module and the designated                                           receiver module.                                                           (e) Bit P is a parity bit generated by                                             the requesting active module which                                             is checked by apparatus included                                               within the SIU 100.                                               MITS 0-3, P                                                                               The four multiport identifier to SIU                                           lines extend from active module to the                                         SIU 100. These lines are coded to indi-                                        cate which subchannel or port within an                                        active module caused the setting of line                                       AOPR.                                                               ARA        The active request accepted line extends                                       from the SIU 100 to each of the active                                         modules. This line is set to indicate                                          that the designated receiving module has                                       accepted the active module's request                                           which allows the active module to remove                                       the requested information from the data                                        interface lines.                                                    ARDA       The accept read data line extends from                                         the SIU to each of the active modules.                                         This line is set by the SIU 100 to indi-                                       cate to the active module that it is to                                        accept the previously requested data from                                      a designated module.                                                DFS 00-35, P0-P3                                                                          The data from SIU lines are another set                                        of data path lines which are a four byte                                       wide unidirectional path (four 10 bit                                          bytes) which extends from the SIU to each                                      active module. These sets of lines are                                         used by the SIU 100 to convey read type                                        data to a designated one of the active                                         modules.                                                            MIFS 0-3, P                                                                               The four multiport identifier lines plus                                       odd parity line extend from the SIU 100                                        to each of the active modules. These                                           lines are coded to indicate which port                                         or subchannel on the active module is to                                       accept the data of a previous read opera-                                      tion from the SIU 100.                                              DPFS       The double precision from SIU line extends                                     from the SIU to each of the active modules.                                    The state of this line indicates whether                                       one or two words of read data are to be                                        accepted by the active module to complete                                      a transfer (read command).                                          AST        The accept status line extends from the                                        SIU 100 to each active module. The state                                       of this line which is mutually exclusive                                       of line ARDA, signals the active module                                        that it should accept status information                                       applied to the DFS lines.                                           ______________________________________                                    

The lines of the programmable interface 601 shown in FIG. 5b provide for transfer of command information from an active module and a designated module. The transfer is accomplished by controlling the logic of states of the various signal lines in accordance with pre-established rules implemented through a sequence of signals termed dialog. The programmable interface includes an accept programmable interface command line (APC), a plurality of programmable interface data from SIU lines (PDFS 00-35, P0-P3), a programmable interface ready line (PIR), a read data transfer request line (RDTR), a plurality of programmable interface data to SIU lines (PDTS 00-35, P0-P3) and a read data accepted line (RDAA). The description of the interface lines are given in greater detail herein.

    ______________________________________                                                  PROGRAMMABLE INTERFACE LINES                                          Designation Description                                                        ______________________________________                                         APC         The accept programmable interface command                                      line extends from the SIU 100 to each re-                                      ceiving module. When set, this line sig-                                       nals the module that command information                                       has been applied to the PDFS lines of the                                      interface by the SIU and is to be accepted                                     by the module.                                                     PDFS 00-35, P0-P3                                                                          The programmable interface data from SIU                                       lines are a four byte wide unidirectional                                      path (four 10 bit bytes) that extend from                                      the SIU 100 to each module. These lines                                        apply programmable interface information                                       from the system interface unit to a desig-                                     nated receiving module.                                            PIR         The programmable interface ready line                                          extends from each module to the SIU.                                           When set, this line indicates that the                                         module is ready to accept a command to                                         be applied to line PDFS.                                           PDTS 00-35, P0-P3                                                                          The programmable interface data to the                                         SIU lines are a four byte wide unidirec-                                       tional path (four 10 bit bytes) that ex-                                       tends from each module to the SIU 100.                                         These lines are used to transfer pro-                                          grammable interface information to the                                         SIU.                                                               RDTR        The read data transfer request line ex-                                        tends from each module connected to the                                        programmable interface to the SIU 100.                                         When set, this line indicates that the                                         previously requested read data is avail-                                       able for transfer to a module and has                                          been applied to the lines PDTS by the                                          module.                                                            RDAA        The read data accepted line extends from                                       the SIU 100 to each module. When set,                                          the line indicates to the module that the                                      data appllied to the lines PDTS has been                                       accepted and that the module may remove                                        the information from these lines.                                  ______________________________________                                    

A further interface is the interrupt interface 602 of FIG. 5c which provides for interrupt processing by the input/output processor 200. That is, the interface enables the transfer of interrupt information by an active module to the SIU 100 as well as the transfer of interrupt information by the SIU 100 to the input/output processor 200 for processing. Similar to the other interfaces, the transfer of interrupt requests is accomplished by controlling the logical states of the various signal lines in accordance with pre-established rules implemented through a sequence of signals termed "dialog".

The interface includes an interrupt request line (IR), a plurality of interrupt data lines (IDA 00-11, P0-P1) and a plurality of interrupt multiport identifier lines (IMID 00-03) for modules connected to ports A through L. For modules connected to ports G and H, the interrupt interface further includes a level zero present line (LZP), a higher level interrupt present line (HLIP), an interrupt data request line (IDR), a release line (RLS) and a plurality of active interrupt level lines (AIL 0-2). As seen from FIG. 5c, the interrupt interface ports G and H do not include an interrupt multiport identifier line. The description of the interrupt interface lines are given in greater detail herein.

    ______________________________________                                                 INTERRUPT INTERFACE LINES                                              Designation                                                                              Description                                                          ______________________________________                                         IR        The interrupt request line extends from                                        each module to the SIU 100. When set,                                          this line indicates to the SIU that it                                         requires service.                                                    IDA 0-3, P0                                                                              The interrupt data lines extend from an                              IDA 4-11, P1                                                                             active module to the SIU 100. These                                            lines are coded to contain control in-                                         formation required to be transferred to                                        the input/output processor when an                                             interrupt request has been accepted by                                         the processor. These bits are coded                                            as follows:                                                                  (a) The state of bit 0 specifies to the                                            SIU 100 which of the two processors                                            (i.e., processor number) is to                                                 process the interrupt request.                                             (b) Bits 1-3 are coded to indicate the                                             priority or level number of the                                                interrupt request to the SIU 100.                                          (c) Bit P0 is a parity bit for bits                                                0-3.                                                                       (d) Bits 4-8 are coded to provide a por-                                           tion of an address required to be                                              generated by the input/output pro-                                             cessor 200 for referencing the                                                 correct procedure for processing                                               the interrupt (i.e., an interrupt                                              control block number ICBN).                                                (e) Bit P1 is a parity bit for bits 4-11.                              IMID 00-03                                                                               The interrupt multiport identifier lines                                       extend from each active module to the SIU                                      100. These lines are coded to identify                                         which specific subchannel of the active                                        module has requested interrupt service.                              LZP       The level zero present line extends from                                       the SIU 100 to the input/output processor                                      200. When set, this line indicates that                                        there is a highest priority (level 0 inter-                                    rupt) request being directed to the proces-                                    sor 200 by the SIU 100.                                              HLIP      The higher level interrupt present line                                        extends from the SIU to the input/output                                       processor. When set, this line indicates                                       that there is an interrupt request having                                      a higher level or priority than the proce-                                     dure or process being executed by the                                          processor 200.                                                       IDR       The interrupt data request line extends                                        from the input/output processor 200 to                                         the SIU 100. When set, this line indi-                                         cates that interrupt data is to be sent                                        to the processor on lines DFS by the SIU                                       100.                                                                 RLS       The release line extends from the input/                                       output processor 200 to the SIU 100. This                                      line when set indicates that the processor                                     200 has completed execution of the current                                     procedure.                                                           AIL 0-2   The active interrupt level lines extend                                        from the SIU to the input/output processor                                     200. These lines are coded to designate                                        the interrupt level number of the procedure                                    being executed by the processor 200.                                 ______________________________________                                    

A next set of interface lines utilized by certain ones of the modules of FIG. 1 corresponds to the local memory interface lines of FIG. 5d. The local memory interface 603 provides for exchanging information between local memory 500 and the modules of the system. The exchange is accomplished by controlling logical states of the various signal interface lines in accordance with pre-established rules implemented through a sequence of signals termed a "dialog". The local memory interface includes a plurality of data to memory lines (DTM 00-35, P0-P3), a plurality of request identifier to memory lines (RITM 0-7, P0-P1), a plurality of specification lines to memory lines (SLTM 0-3, P), an accept P1 command line (APC), an accept ZAC command line (AZC), a P1 interface ready line (PIR), a ZAC interface ready line (ZIR), a read data transfer request line (RDTR), a plurality of data from memory lines (DFM 00-35, P0-P3), a plurality of request identifier from memory lines (RIFM 0-7, P0-P1), a double precision from memory lines (DPFM), a QUAD line, a read data accepted line (RDAA) and a system clock line (SYS-CLK).

Memory and programmable interface commands are transferred out of the same physical data lines of the interface. The interface does not include a set of lines for processing interrupt requests and therefore the modules connected to the local memory by the SIU 100 cannot directly cause a memory interrupt. The description of the local memory interface lines are given in greater detail herein.

    ______________________________________                                         LOCAL MEMORY INTERFACE LINES                                                   Designation                                                                               Description                                                         ______________________________________                                         DTM 00-35, The data path lines constitute a four                               P0-P3      byte wide unidirectional path (36 in-                                          formation lines and four odd parity                                            lines) that extends from the SIU 100 to                                        the local memory 500. These lines are                                          used to transfer memory or programmable                                        interface commands to the local memory                                         500.                                                                RITM 0-3, P0                                                                              The requestor identifier to memory lines                            RITM 4-7, P1                                                                              constitute two groups of four lines which                                      extend from the SIU 100 to the local mem-                                      ory 500. These lines are coded to convey                                       information to the local memory identify-                                      ing the module which initiated the command                                     and are used to return the data requested                                      to the proper module.                                               SLTM 0-3, P                                                                               The specification lines to memory extend                                       from the SIU 100 to the local memory 500                                       and include two port number selection                                          lines, a read/write to memory line, a double                                   precision to memory line and a parity                                          line. The information signals applied to                                       these lines are coded as follows.                                            (a) Bits 0-1 are port number selection                                             bits coded to specify which port or                                            subchannel within the attached mod-                                            ule is to receive or interpret the                                             memory command sent to the module.                                         (b) Bit 2 is a read/write to memory bit                                            which is included in the steering                                              control information received from                                              the active module which is forwarded                                           by the SIU to the local memory 500                                             when a new command is sent to the                                              memory by the SIU 100. The state                                               of this bit indicates the direction                                            of data transfer.                                                          (c) Bit 3 is a double precision to memory                                          bit coded to specify the amount of                                             data to be transferred. It is also                                             included in the steering control in-                                           formation provided by the active                                               module which is forwarded to the                                               local memory module 500 by the SIU                                             100 when a new command is sent to                                              the memory module.                                                AZC        The accept ZAC command line extends from                                       the SIU 100 to the local memory module                                         500. When set, this line signals the                                           local memory module 500 to accept the ZAC                                      command and control information applied                                        to the other lines by the SIU 100. The                                         setting of this interface line is                                              mutually exclusive with the accept P1                                          command interface line.                                             APC        The accept programmable interface command                                      line, as described in connection with the                                      programmable interface, extends from the                                       SIU 100 to the local memory module 500.                                        When set, this line indicates that the                                         command information applied to the lines                                       DTM is to be accepted by the local memory                                      module 500.                                                         PIR/ZIR    The programmable interface ready line/ZAC                                      interface ready line extends from the local                                    memory module 500 to the SIU 100. When set,                                    each line signals the SIU 100 that the local                                   memory module 500 is capable of accepting a                                    programmable interface (PI)/memory (ZAC)                                       command.                                                            RDTR       The read data transfer request line ex-                                        tend from the local memory module 500 to                                       the SIU 100. This line when set indicates                                      that the read type data previously re-                                         quested by a ZAC or PI command is avail-                                       able along with the necessary control in-                                      formation to be sent to the module request-                                    ing the data.                                                       DFM 00-35, P0-P3                                                                          The data from memory lines are a four byte                                     wide unidirectional bus which extends                                          from the local memory module 500 to the                                        SIU 100. These lines are used to return                                        read requested type data to an active                                          module via the SIU 100.                                             RIFM 0-3, P0,                                                                             The two groups of requestor identifier                              RIFM 4-7, P1                                                                              from memory lines extend from the local                                        memory module 500 to the SIU 100. These                                        lines are coded for directing the read                                         data back from module 500 to the request-                                      ing module.                                                         DPFM and QUAD                                                                             The double precision from memory line and                                      QUAD line extend from the local memory                                         module 500 to the SIU 100. These lines                                         are coded to indicate the number of words                                      to be transferred via the SIU 100 to the                                       requesting module during read data trans-                                      fer request time interval. These lines                                         are coded as follows:                                                        QUAD  DPFM                                                                     0     0       one word, single precision                                       0     1       two words, double precision                                      1     X                                                                          (don't care)                                                                           four words                                                  DSD         The read data/status identifier line ex-                                       tends from the local memory module 500                                         to the SIU. The state of this line sig-                                        nals the SIU 100 whether the information                                       applied to the lines DFM is read data or                                       status information when line RDTR is set.                                      When set, the line indicates status in-                                        formation of one or two words (QUAD=O) is                                      being transferred. When reset to a bin-                                        ary ZERO, the line signals that up to                                          four words of data are being transferred,                                      the number being specified by the coding                                       of lines QUAD and DPFM.                                            RDAA        The read data accepted line as mentioned                                       in connection with the programmable                                            terminal extends from the SIU 100 to the                                       local memory module. When set, this                                            line signals the memory module that the                                        data applied on the interface lines by                                         the local memory module has been accepted                                      and that the local memory module may re-                                       move data from these lines.                                        SYS-CLK     The system clock line is a line which ex-                                      tends from the SIU 100 to each module of                                       the system. This line is connected to a                                        clock source included within the input/                                        output processor 200 to synchronize the                                        operations of each memory module from a                                        common system clock source.                                        ______________________________________                                    

A last set of interface lines utilized as an internal interface between the cache unit 750 and central processor 700 corresponds to the cache/CPU interface lines of FIG. 5e. The interface 604 provides for exchanging information and control signals between the processor 700 and the cache unit 750. The exchange is accomplished by controlling the logical states of the various signal interface lines. The cache/CPU interface includes a plurality of data to processor lines (ZDI 0-35, P0-P3), a plurality ZAC and write data lines (ZADO 0-23, RADO 24-35, P0-P3), a processor request signal line (DREQ-CAC), a plurality of cache command lines (DMEM 0-3), a hold cache line (HOLD-C-CU), a cancel line (CANCEL-C), a flush line (CAC-FLUSH), a read request line (RD-EVEN), a read instruction buffer line (RD-IBUF), a read data buffer line (DRDB), an initialization pointer line (INIT-IBUF), a plurality of instruction lines (ZIB0-35, P0-P3), a plurality of address pointer lines (ASFA 32-33), a control line (DSZ), a read I-buffer data line (RD-IBUF/ZDI), a plurality of zone bit lines (DZD 0-3), a bypass cache line (BYP-CAC), a write signal line (WRT-SGN), an instruction buffer empty line (IBUF-EMPTY), an instruction buffer ready line (IBUF-RDY), an instruction buffer full line (IBUF-FULL), a CP stop line (CP-STOP), and a CP control line (DATA-RECOV).

Instructions, cache commands and data are forwarded to the cache unit 750 via different ones of these lines. Additionally, the operation of the processor 700 is enabled or disabled by certain ones of these lines as explained herein. The description of the CPU/cache interface lines are given in greater detail herein.

    ______________________________________                                         CP/CACHE INTERFACE LINES                                                       Designation                                                                               Description                                                         ______________________________________                                         DREQ-CAC   This line extends from the processor 700                                       to cache unit 750. When the DREQ-CAC is                                        set to a binary ONE, a ZAC command is                                          transferred to the cache 750. In the                                           case of a write ZAC command, write data                                        words are transferred in the one or two                                        cycles following the ZAC command and data                                      words are sent from the processor 700                                          through the cache 750 without modifica-                                        tion, to the SIU 100.                                               DMEM 0,1,2,3                                                                              These lines extend from the processor 700                                      to cache 750. These lines are coded to                                         designate the command that the cache 750                                       is to execute. The coding is as follows:                                       DMEM=0000 no op No action is taken and                                         no cache request is generated.                                                 DMEM=0001 Direct The direct command                                            enables the processor 700 to perform a                                         direct transfer of an operand value                                            without action on the part of the cache                                        750. Hence, no cache request is                                                generated by this type of command.                                             DMEM=0010 0-3 - Address Wraparound                                             Command (ADD-WRAP) The address wrap-                                           around command is executed in 2 cycles.                                        At the start of the first cycle, data                                          and command information is transferred                                         to the cache 750. The processor 700 is                                         then turned off before the next clock                                          interval. During the second cycle, the                                         processor is turned on and at the                                              end of the cycle the data given to it is                                       made available to the processor 700.                                           DMEM=0100 0-3 - Load Instruction Buffer                                        instruction Fetch 1 (LD-IBUF-IF1) The                                          load instruction buffer command is exe-                                        cuted in one cycle. At the start of the                                        cycle, address and command information is                                      transferred to the cache 750. At the                                           end of the cycle, the block specified by                                       the address is written into the instruc-                                       tion buffer at a previously designated                                         instruction buffer address, and the                                            addressed word is transferred to the                                           processor 700 via the ZDI lines 0-35.                                          DMEM=0101 0-3 - Load Instruction Buffer                                        Instruction Fetch 2 (LD-IBUF-IF2) The                                          load instruction buffer comnand is exe-                                        cuted in one cycle. At the start of the                                        cycle, address and command information is                                      transferred to the cache 750. At the                                           end of the cycle, the block specified by                                       the address is written into the instruc-                                       tion buffer at the previously designated                                       instruction buffer address.                                                    DMEM=0110 - Load Quad                                                          The load quad is executed in one cycle.                                        Same as IF2 but data goes to another                                           portion of the I Buffer.                                                       DMEM=0111 0-3 - Preread (PR-RD) The                                            preread command is executed in a variable                                      number of cycles with a minimum of one.                                        At the start of the first cycle, address                                       and command information are transferred                                        to cache 750. During the first cycle,                                          when the address specified is that of a                                        block which is in the cache 750, the pre-                                      read operation terminates and no other                                         action is taken. If the addressed block                                        is not in the cache 750, then at the end                                       of the first cycle, the request is trans-                                      ferred to the main memory. When the re-                                        quested block has been read from main                                          memory, the data is stored in the cache                                        750.                                                                           DMEM=1000 0-3 - Read Single (RD-SNG)                                           The read single command is executed in one                                     cycle. At the start of the cycle, address                                      and command information are given to the                                       cache 750 and at the end of the cycle the                                      data made available to processor 700.                                          DMEM=1001 0-3 - Read Clear (RD-CLR)                                            The read clear command is executed in a vari-                                  able number of cycles with a minimum of 9.                                     At the start of the first cycle, address                                       and command information are transferred                                        to the main memory, and the processor is                                       turned off. During the second cycle, when                                      the addressed word is contained in a                                           cache the block containing the word is                                         fetched from the cache 750. When the re-                                       quested word has been read from main                                           memory and transferred to the cache 750,                                       then the processor is turned on.                                               DMEM=1010 0-3 - Read Double Odd                                                (RD-DBL-φ)                                                                 (line DSZ is a binary ZERO) The read                                           double odd command is executed in two                                          cycles. At the start of the first cycle,                                       address and command information are                                            transferred to the cache 750. At the                                           end of the first cycle, the word at the                                        odd address is made available to the pro-                                      cessor 700. At the end of the second                                           cycle, the word at the even address is                                         made availabe to the processor.                                                DMEM=1010 0-3 - Read Double Even                                               (RD-DBL-E)                                                                     (line DSZ is a binary ONE) The read                                            double even command is executed in two                                         cycles. At the start of the first cycle,                                       address and command information are                                            transferred to cache 750. At the end of                                        the first cycle the word at the even                                           address is made available to the processor                                     700. At the end of the second cycle,                                           the word at the odd address is made                                            available to the processor 700.                                                DMEM=1011 0-3 - Read Remote (RD-RMT)                                           The read remote command is executed in a                                       variable number of cycles, with a minimum                                      of 10. At the start of the first cycle,                                        address and command information are                                            transferred to cache 750. At the end of                                        the first cycle, the request is trans-                                         ferred to the main memory and the pro-                                         cessor 700 is turned off. When the re-                                         quested word pair has been fetched from                                        memory, processor 700 is turned on and                                         the data is made available to it.                                              DMEM=1100 0-3 - Write Single                                                   (WRT-SNG)                                                                      The write single command is executed in                                        two cycles. At the start of the first                                          cycle, address and command information                                         is transferred to the cache 750. At the                                        start of the second cycle, the data is                                         transferred to the cache 750. During the                                       second cycle, the data is written into                                         the cache 750, if the block which contains                                     the addressed word is stored in the cache                                      750. During the end of the second cycle,                                       the write request and the data is trans-                                       ferred to the main memory.                                                     DMEM=1110 0-3 - Write Double                                                   (WRT-DBL)                                                                      The write double command is executed in                                        three cycles. At the start of the first                                        cycle, address and command information                                         are transferred to the cache 750. At                                           the start of the second (third) cycle                                          the even (odd) data word is transferred                                        to the cache 750. During the third cycle,                                      the data is written into the cache, if                                         the block which contains the addressed                                         word pair is stored in the cache 750.                                          At the end of the third cycle, the write                                       request and both data words will have                                          been passed on to the main memory.                                             DMEM=1111 0-3 - Write Remote                                                   (WRT-RMT)                                                                      The write remote command is executed in                                        three cycles. At the start of the first                                        cycle, address and command information                                         are transferred to the cache 750. At                                           the end of the first cycle, the request                                        is transferred to the main memory. Dur-                                        ing the next two cycles, the 2 data words                                      are transferred to the cache 750 which                                         transfers same to main memory.                                      HOLD-C-CU  This line extends from processor 700 to                                        cache 750. When set to a binary ONE, this                                      control signal specifies that the cache                                        750 is to assume a HOLD state for re-                                          quests or data transfers.                                           CANCEL-C   This line extends from processor 700 to                                        cache 750. When set to a binary ONE, this                                      control signal aborts any request made to                                      cache 750.                                                          CAC-FLUSH  This line extends from processor 700 to                                        cache 750. When set to a binary ONE, it                                        starts a flush of the cache 750.                                    RD-EVEN    This line extends from processor 700 to                                        cache 750. When the cache makes a double                                       word request to the SIU, the even word                                         is saved in a special register. When                                           RD-EVEN line is set to a binary ONE, the                                       contents of this register is gated onto                                        the ZDI lines.                                                      ZAD0 0-23, These 40 unidirectional lines extend from                           RAD0 24-35 processor 700 to cache 750. The lines                               P0-P3      are used to transfer ZAC command and                                           write data words to the cache 750.                                  RD-IBUF    This line extends from the processor 700                                       to cache 750. When set to a binary ONE,                                        the line causes an instruction buffer                                          out pointer to increment for                                                   processing a next instruction in accordance                                    with the state of a line DRDB as follows.                           DZD 0-3    These four lines extend from processor 700                                     to cache 750. These lines transfer odd                                         word zone bit signals for write double                                         commands.                                                           BYP-CAC    This line extends from processor 700 to                                        cache 750. When set to a binary ONE, this                                      line causes the cache 750 to request data                                      words from main memory for read type in-                                       structions.                                                         WRT-SGN    This line extends from the cache 750 to                                        processor 700. It is used to signal the                                        processor 700 during write commands that                                       the cache 750 has completed the transfer                                       of ZAC commands and data words to the SIU                                      100.                                                                ASFA 32-33 These two lines extend from processor 700                                      to cache 750. These lines are coded to                                         specify the next word of a block stored in                                     the I buffer to be read out to the processor                                   700 when the I buffer is initialized under                                     hardware control via the INIT IBUF line.                            INIT-IBUF  The initialize instruction buffer                                              command is executed in one cycle. At                                           the end of the cycle, a buffer in pointer                                      is reset to ZEROS and the buffer out                                           pointer is loaded with an initial value.                            DSZ1       This line extends from the processor                                           750 to cache 750. The state of this line                                       specifies to cache 750 the order in which                                      words are to be set to the processor 700                                       when a read double command is performed.                            DRDB100    This line extends from the processor                                           700 to cache 750. It is used as the                                            most significant bit of the I Buffer read                                      address.                                                            RD-IBUF/ZDI                                                                               This line extends from processor 700 to                                        cache 750. It causes the cache 750 to                                          apply the data on the ZIB lines to the                                         ZDI lines.                                                          ZDI 0-35   These 40 unidirectional lines extend from                           P.sub.0, P.sub.1, P.sub.2, P.sub.3                                                        cache 750 to processor 700. They apply                                         data from the cache 750 to the processor                                       700.                                                                ZIB 0-35   These 40 unidirectional lines extend from                           P.sub.0, P.sub.1, P.sub.2, P.sub.3                                                        cache 750 to processor 700. They apply                                         instructions from the cache Instruction                                        Buffer to the processor 700.                                        I BUF-EMPTY                                                                               This line extends from cache 750 to pro-                                       cessor 700. When set to a binary ONE,                                          this line indicates that the Instruction                                       Buffer contains no instructions at this                                        time.                                                               I BUF-RDY  This line extends from cache 750 to pro-                                       cessor 700. When set to a binary ONE,                                          the line indicates that the Instruction                                        Buffer contains at least one instruction.                           I BUF-FULL This line extends from cache 750 to pro-                                       cessor 700. This line indicates that the                                       Instruction Buffer contains more than                                          four instructions or it has at least one                                       instruction and an outstanding instruction                                     fetch request line.                                                 CP STOP    This line extends from cache 750 to pro-                                       cessor 700. When forced to a binary ONE                                        state, the line signals that as a result                                       of special conditions detected within                                          the cache unit 750, the processor 700 is                                       required to wait or halt its operation                                         while the cache unit 750 resolves the                                          special conditions.                                                 DATA-RECOV This line extends from the cache 750                                           to processor 750. It is used to re-                                            strobe processor registers following                                           the stopping of the processor 700 in                                           response to the detection of a cache                                           miss condition.                                                     ______________________________________                                    

While FIGS. 5a through 5e show lines which connect the different modules of the system of FIG. 1 to SIU 100 in addition to the connection to processor 700 and cache unit 750, it will be appreciated that other lines are also included for signalling other conditions, as for example, certain error conditions and operational conditions. For further descriptions of the various modules of FIG. 1, reference may be made to U.S. Pat. No. 4,000,487. Now, the processor module 700 and cache unit 750 will be described in greater detail.

GENERAL DESCRIPTION OF PROCESSOR 700-FIG. 2

Referring to FIG. 2, it is seen that the host processor 700 includes an execution control unit 701, a control unit 704, an execution unit 714, a character unit 720, an auxiliary arithmetic and control unit (AACU) 722, a multiply-divide unit 728, which are interconnected as shown. Additionally, the control unit 704 has a number of interconnections to the cache unit 750 as shown.

The execution control unit 701 includes an execution control store address preparation and branch unit 701-1, and an execution control store 701-2. The store 701-2 and unit 701-1 are interconnected via buses 701-3 and 701-6 as shown.

The control unit 704 includes a control logic unit 704-1, a control store 704-2, an address preparation unit 704-3, data and address output circuits 704-4, an XAQ register section 704-5 which interconnect as shown.

As seen from FIG. 2, the SIU interface 600 provides a number of input lines to the cache unit 750. The lines of this interface have been described in detail previously. However, in connection with the operation of cache unit 750, certain ones of these lines are specially coded as follows.

1. MITS 0-3 for Reads are coded as follows:

bits 0-1=00;

bits 2-3=Read ZAC buffer address;

For Write Operation bit 0-3=Odd word zone

2. MIFS lines are coded as follows:

bit 0=0;

bit 1=0 even word pairs (words 0,1);

bit 1=1 odd word pairs (words 2,3);

bits 2-3=ZAC buffer address to memory.

As concerns the interface lines DFS 00-35, P0-P3, these lines convey read data to cache unit 750. The lines DTS 00-35, P0-P3, are used to transfer data from cache 750 to the SIU 100.

The control unit 704 provides the necessary control for performing address preparation operations, instruction fetching/execution operations and the sequential control for various cycles of operation and/or machine states. The control is generated by logic circuits of block 704-1 and by the execution control unit 701 for the various portions of the control unit 704.

The XAQ register section 704-5 includes a number of program visible registers such as index registers, an accumulator register, and quotient register. This section will be discussed in greater detail with reference to FIG. 3. Other program visible registers such as the instruction counter and address registers are included within the address preparation unit 704-3.

As seen from FIG. 2, the section 704-5 receives signals from unit 704-3 representative of the contents of the instruction counter via lines RIC 00-17. Also, lines ZRESA 00-35 apply output signals from the execution unit 714 corresponding to the results of operations performed upon various operands. The section 704-5 also receives an output signal from the auxiliary arithmetic and control unit via lines RAAUO-8.

The section 704-5 provides signals representative of the contents of one of the registers included within the section as an input to the address preparation unit 704-3. The address preparation unit 704-3 forwards the information through a switch to the execution unit 714 via the lines ZDO 0-35. Similarly, the contents of certain ones of the registers contained within section 704-5 can be transferred to the execution unit 714 via the lines ZEB 00-35. Lastly, the contents of selected ones of these registers can be transferred from section 704-5 to the multiply/divide unit 728 via the lines ZAQ 00-35.

The address preparation unit 704-3 generates addresses from the contents of various registers contained therein and applies the resultant logical, effective and/or absolute addresses for distribution to other units along the lines ASFA 00-35. The address preparation unit 704-3 receives the results of operations performed on a pair of operands by the execution unit 714 via the lines ZRESB 00-35. The unit 704-3 receives signals representative of the contents of a pair of base pointer registers from the control logic unit 701 via the lines RBASA and RBASB0-1. Outputs from the multiply/divide unit 728 are applieid to the address preparation unit 704-3. Lastly, the contents of a secondary instruction register (RSIR) are applied as input to the unit 704-13 via the lines RSIR 00-35.

The data and address output circuits 704-4 generate the cache memory address signals which it applies to the cache unit 750 via the lines RAD0/ZAD0 00-35. These address signals correspond to the signals applied to one of the sets of input lines ZDI 00-35, ASGA 00-35 and ZRESB 00-35 selected by switches included within the circuits of block 704-4. Also, word address signals are applied via the lines ASFA 32-33. These circuits will be further discussed herein in greater detail.

The control logic unit 704-1 provides data paths which have an interface with various units included within the cache unit 750. As described in greater detail herein, the lines ZIB 00-35 provide an interface with an instruction buffer included within the cache 750. The lines ZDI 00-35 are used to transfer data signals from the cache 750 to the control logic unit 704-1. Other signals are applied via the other data and control lines of the cache-CP interface 604. These lines include the CP stop line shown separately in FIG. 2.

As seen from FIG. 2, the control logic unit 704-1 provides a number of groups of output signals. These output signals include the contents of certain registers, as for example, a basic instruction register (RBIR) whose contents are applied as an input to control store 704-2 via the lines RBIR 18-27. The control logic unit 704-1 receives certain control signals read out from control store 704-2 via the lines CCSD0 13-31.

The control logic unit 704-1 also includes a secondary instruction register (RSIR) which is loaded in parallel with the basic instruction register at the start of processing an instruction. The contents of the secondary instruction register RSIR 00-35, as previously mentioned, are applied as inputs to the address preparation unit 704-3. Additionally, a portion of the contents of the secondary instruction register are applied as inputs to the auxiliary arithmetic control unit 722 via the lines RSIR 1-9 and 24-35.

The control store 704-2 as explained herein provides for an initial decoding of program instruction op-codes and therefore is arranged to include a number of storage locations (1024), one for each possible instruction op-code.

As mentioned, signals applied to lines RBIR 18-27 are applied as inputs to control store 704-2. These signals select one of the possible 1024 storage locations. The contents of the selected storage location are applied to the lines CCSD0 13-31 and to CCSD0 00-12 as shown in FIG. 2. The signals supplied to lines CCSD0 00-12 correspond to address signals which are used to address the execution control unit 701 as explained herein.

The remaining section of processor 700 will now be briefly described. The execution unit 714 provides for instruction execution wherein unit 714 performs arithmetic and/or shift operations upon operands selected from the various inputs. The results of such operations are applied to selected outputs. The execution unit 714 receives data from a data input bus which corresponds to lines RDI 00-35 which have as their source the control logic unit 704-1. The contents of the accumulator and quotient registers included within section 704-5 are applied to the execution unit 714 via the lines ZEB 00-35 as mentioned previously. The signals applied to the input bus lines ZDO 00-35 from the address preparation unit 704-3 are applied via switches included within the execution unit 714 as output signals to the lines ZRESA 00-35 and ZRESB 00-35, as shown in FIG. 2. Additionally, execution unit 714 receives a set of scratch pad address signals from the auxiliary arithmetic and control unit 722 applied via the lines ZRSPA 00-06. Additionally, the unit 722 also provides shift information to the unit 714 via the lines ZRSC 00-05.

The character unit 720 is used to execute character type instructions which require such operations as translation and editing of data fields. As explained herein, these types of instructions are referred to as extended instruction set (EIS) instructions. Such instructions which the character unit 720 executes include the move, scan, compare type instructions. Signals representative of operands are applied via lines ZRESA 00-35. Information as to the type of character position within a word and the number of bits is applied to the character unit 720 via the input lines ZDB 00-07.

Information representative of the results of certain data operations is applied to the unit 722 via the lines ZOC 00-08. Such information includes exponent data and data in hexadecimal form. The character unit 720 applies output operand data and control information to the unit 722 and the unit 728 via the lines RCHU 00-35.

The auxiliary arithmetic and control unit 722 performs arithmetic operations upon control information such as exponents used in floating point operations, calculates operand lengths and pointers and generates count information. The results of these operations are applied to execution unit 714 via the lines ZRSPA 00-06 and lines ZRSC 00-06 as mentioned previously. Information signals corresponding to characters such as 9-bit characters, 6-bit characters, decimal data converted from input hexadecimal data, quotient information and sign information are applied to section 704-5 via the lines RAAU 00-08.

As seen from FIG. 2, the unit 722 receives a number of inputs. Character pointer information is applied via the lines ASFA 33-36. EIS numeric scale factor information and alphanumeric field length information are applied to the unit 722 via the lines RSIR 24-35. Other signals relating to fetching of specific instructions are applied via the lines RSIR 01-09. Exponent signals for floating point data are applied to the unit 722 via the lines ZOC 00-08 while floating point exponent data signals from unit 704-1 are applied via the lines RDI 00-08. Shift count information signals for certain instructions (e.g. binary shift instructions) are applied to the unit via the lines RDI 11-17. As concerns the input signals applied to the lines RCHU 00-35, lines 24-35 apply signals corresponding to the length of EIS instruction fields while 18-23 apply address modification signals to the unit 722.

The last unit is the multiply/divide unit 728 which provides for high-speed execution of multiply and divide instructions. This unit may be considered conventional in design and may take the form of the multiply unit described in U.S. Pat. No. 4,041,292 which is assigned to the same assignee as named herein. The unit 728 as seen from FIG. 2 receives multiplier dividend and divisor input signals via the lines RCHU 00-35. The multiplicand input signals from register section 704-5 are applied via the lines ZAQ 00-35. The results of the calculations performed by the unit 728 are applied as output signals to the lines ZMD 00-35.

As mentioned previously, the cache unit 750 transfers and receives data and control signals to and from the SIU 100 via the data interface line 600. The cache unit 750 transfers and receives data and control signals to and from the processor 700 via the lines of interface 604. Lastly, the cache unit 750 receives address and data signals from the circuits 704-4 via the lines RAD0/ZAD0 00-35 and the lines ASFA 32-33.

DETAILED DESCRIPTION OF THE PROCESSOR 700

The various sections which comprise the processor 700 illustrated in FIG. 2 will now be discussed in greater detail with respect to FIGS. 3a through 3i.

Referring to FIGS. 3a and 3b, it is seen that the processor includes two control stores: (1) the control unit control store (CCS) 704-200 which forms part of the control unit 704; and (2) the execution control store (ECS) 701-2 which is included within the execution control unit 701.

The cache oriented processor 700 of the preferred embodiment of the present invention includes a three stage pipeline. This means that the processor 700 requires at least three processor cycles to complete the processing of a given program instruction and can issue a new instruction at the beginning of each cycle. Hence, a number of program instructions may be in some stage of processing at any given instant of time.

In the preferred embodiment of the processor 700 includes the following stages: an instruction cycle (I) wherein instruction interpretation, op-code decoding and address preparation take place; a cache cycle (C) wherein access to the cache unit 750 is made ensuring high performance operation; and, an execution cycle (E) wherein instruction execution takes place under microprogram control.

As concerns control, during the I cycle, the op-code of the instruction applied via lines RBIR 18-27 is used to access a location within control store 704-2. During a C cycle, the accessed contents from control store 704-2 are applied to lines CCS D0 00-12 and in turn used to access one of the storage locations of the execution control store 701-2. During the C cycle, the microinstructions of the microprogram used to execute the instruction are read out from the execution control store 701-2 into a 144-bit output register 701-4. The signals designated MEMD0 00-143 are distributed to the various functional units of processor 700. During an E cycle, the processor executes the operation specified by the microinstructions.

Referring specifically to FIG. 3a, it is seen that the control store 704-2 includes a control unit control store (CCS) 704-200 which is addressed by the op-code signals applied to the lines RBIR 18-27. The CCS 704-200, as mentioned previously, includes 1024 storage locations, the contents of which are read out into an output register 704-202 during an I cycle of operation. FIG. 6a shows schematically the format of the words stored within the control store 704-200.

Referring to FIG. 6a, it is seen that each control unit control store word includes five fields. The first field is a 13-bit field which contains an ECS starting address location for the instruction having an op-code applied to lines RBIR 18-27. The next field is a three bit field (CCSφ) which provides for the control of certain operations. The bit interpretations of this field depend upon its destination and whether it is decoded by specific logic circuits or decoded under microprogram control. The next field is a 4-bit field which provides for certain register control operations.

The next field is a 6-bit sequence control field which is coded to specify a sequence of operations to be performed under hardwired logic circuit control as well as the type of cache operation. In the present example, this field is coded as 75₈. The last field is a 6-bit indicator field which is not pertinent to an understanding of the present invention.

As seen from FIG. 3a, signals corresponding to the CCSA field of a control unit control store word are applied via a path 704-204 as an input to the execution generation circuits 701-7. Signals corresponding to the CCSR field are applied as an input to the execution unit 714 via path 704-206. Additionally, the same signals are applied as an input to the address preparation unit 704-3 via another path 704-208.

Signals representative of the sequence control field apply as an input to the sequence control logic circuits 704-100 via path 704-210. As explained herein, these circuits decode the sequence control field and generate signals for conditioning the cache unit 750 to perform the operation designated.

As mentioned previously, the execution address generation circuit 701-1 receives an input address which corresponds to field CCSA from the control store 704-2. As seen from FIG. 3b, these circuits include an input address register 701-10 whose output is connected to one position of a four position switch 701-12 designated ZECSA. The output of the switch serves as an address source for the control store 701-2. The first position of the switch 701-12 is connected to receive an address from the MICA register 701-14. The contents of register 701-14 are updated at the end of each cycle to point to the location within the ECS control store following the location whose contents were read out during that cycle.

The second position selects the address produced from the ZCSBRA branch address selector switch 701-18. The third position selects the address of the first microinstruction in each microprogram provided by the CCS control store which is loaded into the REXA register 701-10. When the CCS output is not available at the termination of a microprogram, a predetermined address (octal address 14) is automatically selected.

The first position of branch switch 701-18 receives signals corresponding to a branch address read out from store 701-2 into register 701-4 which is in turn forwarded to a return control register 701-20. The second, third and fourth positions of switch 701-18 receives signals from RSCR register 701-20, an MIC register 701-15 and the contents of a number of vector branch registers 701-36. The MIC register 701-15 stores an address which points to the microinstruction word following the microinstruction word being executed. This address corresponds to address from switch 701-12 incremented by one by an increment circuit 701-12.

The vector branch registers include a 4-bit vector branch register 0 (RVB0), a 2-bit vector branch register 1 (RVB1) and a 2-bit vector branch register 2 (RVB2). These registers are loaded during a cycle of operation with address values derived from signals stored in a number of different indicator flip-flops and registers applied as inputs to the number of groups of input multiplexer selector circuits 701-32 and 701-34. The outputs of the circuits 701-32 and 701-34 are applied as inputs to two position selector circuits 701-30. These circuits in turn generate the output signals ZVBR0, ZVBR1 and ZVBR2 which are stored in the registers 701-36.

The switch 701-36 provides an address based upon the testing of various hardward indicator signals, state flip-flop signals selected via an INDGRP field. The branch decision is determined by masking (ANDING) the selected indicator set with the INDMSKU and INDMSKL fields of a microinstruction word. If a vector branch is selected, INDMSKU is treated as 4 ZERO bits. The "OR" of the 8 bits is compared to the state defined by the TYPG and GO microinstruction fields. The hardware signals are applied via a number of data selector circuits 701-28 only one of which is shown whose outputs are in turn applied as inputs to a further five position multiplexer selector circuit 701-26. The output of the multiplexer circuit 701-26 feeds a comparison circuit which "ands" the indicator signals with the mask signals to produce the resulting signals MSKCBR0-7.

The signals MSKCBR0-7 are applied to another comparison circuit which "ands" the signals with the condition branch test signals TYPGGO to set or reset a branch decision flip-flop 701-22 which produces a signal RBDGO whose state indicates whether branching is to take place. The output signal RBDGO is applied as a control input to the first two positions of switch 701-12. When the branch test condition is not met (i.e., signal RBDGO=0), then the incremented address from the MICA register 701-14 is selected.

In some instances, as seen herein, it is not possible to test the state of an indicator on the cycle following its formation. For this reason, history registers HR0-HR7, not shown, are provided for register storage of the Group 2 indicators. The states of such stored indicators are selected and tested in a manner similar to that of the other indicators (i.e., mask fields).

Additionally, the unit 701-1 includes a number of indicator circuits, certain ones of these are used to control the operation of certain portions of the processor 700 when the strings being processed by certain types of instructions have been exhausted. These indicator circuits are included in block 701-42 and are set and reset under the control of a field within the microinstruction word of FIG. 6a (i.e., IND6 field). The bits of this field read out from the ECS output register 701-4 are applied to an RMI register 701-38 for decoding by a decoder 701-40. Based upon the state of status indicator signals received from the various processor units (e.g. 714, 720, 722, etc.), the appropriate ones of the auxiliary flip-flops are switched to binary ONE states. The outputs of these flip-flops are applied via the different positions of a 4 position switch 701-44 to the GP3 position of switch 701-26 for testing. The same outputs are applied to a second position of a ZIR switch 701-43 for storage via the ZDO switch 704-340. The ZIR switch 701-43 also receives indicator signals from an indicator register (IR) 701-41. This register is loaded via the RDI lines 18-30 and 32 in response to certain instructions.

The indicator status signals for example include the outputs of the different adder circuits (AL, AXP) of the unit 720. These signals will set different ones of a number of exhaust flag flip-flops designated FE11, FE12, FE13, FE1E, FE2E, FE2 and FE3 The FE1E and FE2E flip-flops are set during any FPOA cycle of any instruction. These flip-flops in turn cause the FE11, FE12, and FE13 flip-flops to be set when the outputs from the AL or AXP adder circuits of unit 720. The setting and resetting of these indicators will be described herein in further detail in connection with the description of operation. However, the exhaust flag flip-flops pertinent to the example given herein are set and reset in accordance with the following Boolean expressions.

Set: fe1e=feoa+ind6fld field.

Reset: fe1e=ind6fld field.

Set: fe2e=fpoa+ind6fld field.

Reset: fe2e=ind6fld field.

Set: fe11=ind6fld field·FE1E (ALES +AXPES+DESC1·AP0-4=0) +IND6FLD field·FE1E·DESCl·(AP0-5=0=APZN=ALZN)=IND6FLD field.

Reset: fe11=fpoa+ind6fld field.

Set: fe12=ind6fld field·FE1E·(ALES+AXPES+FE13).

Reset: fe12=fpoa+ind6fld field.

Set: fe13=ind6fld field·FE1E·ALES+IND6FLD field.

Reset: fe13=fpoa+ind6fld field. SET:FE2=IND6FLD field·FE2E·ALES+IND6FLD field·FE2E·DESC2·(APO-4=0+APO-5=0+APZN+ALZN)+(IND6FLD field) FE2E·DESC2+IND6FLD.

Reset: fe2=fpoa+ind6fld field.

Set: fe3=ind6fld field·DESC3·(AP0-4=0+APO-5=0+APZN+ALZN)+IND6FLD field·DESC3+IND6FLD. RESET: FE3=FPOA+IND6FLD field.

Wherein IND6FLD indicates a particular code;

Ales=al=0 or AL-C;

Axpes=axp=0 or AXP-C;

Apzn=ap0-7≦0; and,

Alzn=al0=11≦0.

the ZCSBRA switch 701-18 is normally enabled when the branch decision flip-flop RBD was set to a binary ONE in the previous cycle. The first position selects a 13-bit branch address from the current microinstruction applied via the RSCR register 701-20. The branch address enables any one of the locations of the ECS control store to be addressed directly. The second position selects the concatenation of the 6 low order address bits from the current microinstruction applied bia MIC register 701:15 and the 7 upper bits of the ranch address from the current microinstruction applied via the RSCR register 701:20. This permits branches within a 64-word page defined by the contents of the MIC register 701-15 (current location+1).

The third position selects the concatenation of 4 low order bits from the RVBO vector branch register, 6 bits from the branch field of the current microinstruction stored in RCSR register and the 3 upper bits of the address stored in the MIC register. This permits 16-way branches. The fourth position selects the concatenation of the 2 low order ZEROS with 4 bits from the vector branch register RVBO with the 4 most significant bits of the branch address field of the current microinstruction and the 3 upper bits of the current address stored in the MIC register. This permits 16-way branches with 3 control store locations between each adjacent pair of destination addresses.

The fifth position selects the concatenation of 2 low order ZEROS with 2 bits from vector branch register RVB1, with the 6 bits of the branch address of the current microinstruction and the upper 3 bits from the MIC register. This permits branches with 4 possible destinations with 3 control store locations between each adjacent pair of destination addresses.

The sixth position selects the concatenation of 2 low order ZEROS with 2 bits from vector branch register RVB2 with the 6 bits of the branch address of the current microinstruction and the upper 3 bits from the MIC register. This permits 4-way branches with 3 control store locations between each adjacent pair of destination addresses.

The output of switch 701-12 addresses a specific location within control store 701-2 which causes the read out of a microinstruction word having a format illustrated in FIG. 6b. Referring to that Figure, it is seen that this microinstruction word is coded to include a number of different fields which are used to control the various functional units within processor 700. Only those fields which are related to the present example will be described herein.

    ______________________________________                                         Bits 0-1              Reserved for Future Use.                                 Bit 2    EUFMT        Defines which format the EU                                                    is to operate with. EUFMT-0                                                    specifies a first microinstruc-                                                tion format while EUFMT=1                                                      specifies an alternate micro-                                                  instruction format.                                      Bits 3-5 TRL          TR Low Write Control.                                           Write control of EU temporary registers                                        TR0-TR3.                                                                       OXX    No change                                                               100    Write TR0                                                               101    Write TR1                                                               110    Write TR2                                                               111    Write TR3                                                        Bits 6-8 TRH          TR High Write Control.                                          Write control of EU temporary registers                                        TR4-TR7.                                                                       OXX    No change                                                               100    Write TR4                                                               101    Write TR5                                                               110    Write TR6                                                               111    Write TR7                                                        Bits 9-12                                                                               ZOPA         ZOPA Switch Control.                                            Selects the output of ZOPA switch.                                             0)   0000      TR0                                                             1)   0001      TR1                                                             2)   0010      TR2                                                             3)   0011      TR3                                                             4)   0100      TR4                                                             5)   0101      TR5                                                             6)   0110      TR6                                                             7)   0111      TR7                                                             8-11)                                                                               10XX      RDI                                                             12)  1100      ZEB                                                             13)  1101      ZEB                                                             14)  1110      ZEB                                                             15)  1111      0      (disable)                                         Bits 13-16                                                                              ZOPB         ZOPB Switch Control.                                            Selects the output of ZOPB switch.                                      Bits 17-18                                                                              ZRESA        ZRESA Switch Control.                                           Selects the output of ZRESA switch.                                            00   ALU                                                                       01   Shifter                                                                   10   Scratchpad/RDI switch                                                     11   ZDO                                                                Bits 19-20                                                                              ZRESB        ZRESB Switch Control.                                           Selects the output of ZRESB switch.                                            00   ALU                                                                       01   Shifter                                                                   10   Scratchpad/RDI switch                                                     11   ZDO                                                                Bit 21   RSPB         Scratchpad Buffer Strobe                                                       Control.                                                        Strobes RSPB with ZRESB data.                                                  0    No strobe                                                                 1    Strobe RSPB                                                        Bit 22   RSP          Scratchpad Write Control.                                       0    Read scratchpad                                                           1    Write scratchpad                                                   Bit 23   ZSPDI        Scratchpad/RDI Switch                                                          Control.                                                        Selects the output of the Scratchpad/RDI switch.                               0    Scratchpad output                                                         1    RDI                                                                Bits 24-25                                                                              ZSHFOP       Shifter Operand Switch                                                         Control.                                                        Selects the left operand to the Shifter.                                       00   ZOPA output                                                               01   EIS output                                                                10   0                                                                         11   Select 0 or -1 depending on bit 0 of                                           right operand to Shifter.                                          Bits 24-27                                                                              ALU          ALU Function Control.                                           Selects the operation applied to the two inputs                                (A and B) to the ALU.                                                   Bits 24-29                                                                              N/A                                                                   Bits 26-31                                                                              RFU          Reserved for Future Use.                                 Bits 30-31                                                                              ZALU         ALU Switch Control.                                             Selects the output of ZALU switch.                                      Bits 32-33                                                                              NXTD         Next Descriptor Control.                                        Strobes RBASB and RDESC registers.                                             00     RBASB←00                                                                  RDESC←00                                                           01     RBASB←01                                                                  RDESC←01                                                           10     RBASB←Alt                                                                 RDESC←10                                                           11     No strobes (default)                                             Bits 32-35                                                                              CCM          Control constant field                                                         reference by the CONTF                                                         field.                                                   Bits 34-35                                                                              IBPIPE       IBUF/Pipeline Control.                                          Selects the reading of IBUF or the pipeline                                    operation.                                                                       00       No operation                                                          01       Read IBUF/ZDI (Alt)                                                   10       Type 1 Restart Release or                                             11       Type 4 Restart Wait                                          Bits 36-37                                                                              FMTD                                                                         Selects the loading of various CU registers                                    and indicates the interpretation to be given                                   to the MEMADR field for small CU control.                                      00     No operation                                                            01     RADO←ASFA                                                          10     RADO←ZRESB                                                         11     RADO←ASFA                                                   Bits 38-40                                                                              MEMADR       Cache Control.                                                  Selects cache operations. The complete inter-                                  pretation for this control is a function of the                                FMTD control.                                                                   000   No operation                                                            001    Read Sgl                                                                010    Load Quad                                                               011    Preread                                                                 100    Write Sgl                                                               110    Read Sgl Trans (for FMTD = 11                                                  only)                                                                   111    Write Sgl Word (for FMTD = 11                                                  only)                                                            Bit 41   ZONE         Zone Control.                                                   Indicates zone or no zone for small CU control.                                0      No zone                                                                 1      Zone                                                             Bits 42-44                                                                              TYPA         Type A Flag.                                                    Indicates the type A overlayed fields being                                    used.                                                                          000    Type A=0 fields                                                          .                                                                              .                                                                              .                                                                              .                                                                             100    Type A=4 fields                                                  Bits 44-46                                                                              PIPE         Pipeline Control                                                Selects the type of restart to be initiated.                                   000    No operation                                                            001    Type 1 Restart and Release                                              010    Type 2 Restart                                                          011    Type 3 Restart                                                          100    Type 4 Restart                                                          101    Type 5 Release                                                          110    Type 6 Restart                                                   Bits 44-47                                                                              AUXREG       Auxiliary Register Write                                                       Control                                                         Selects an auxiliary register or combinations                                  to be strobed with data selected by the AUXIN                                  control field.                                                                 0)  0000   No strobe                                                           1)  0001   RRDXA                                                               2)  0010   R29                                                                 3)  0011   R29, RRDXA, FRL, RID                                                4)  0100   RRDXB                                                               5)  0101   RTYP                                                                6)  0110   RBASA                                                               7)  0111   RBASA, RTYP                                                         8)  1000   RBASB                                                               9)  1001   RDESC                                                               10)  RBASA, R29, RRDXA                                                  Bits 45-46                                                                              TYPB         Type B Flag.                                                    Indicates the Type B overlayed fields being                                    used.                                                                          00     Type B = 0 fields                                                        .                                                                              .                                                                              .                                                                              .                                                                             11     Type B = 3 fields                                                Bit 47   RSC          RSC Strobe Control.                                             Strobes the RSC register. (Shift Count)                                 Bit 47   RSPA         RSPA Strobe Control.                                            Strobes the RSPA register.                                              Bits 47-48                                                                              N/A                                                                   Bit 47   RAAU         RAAU Strobe Control.                                            Strobes RAAU register.                                                  Bits 48-49                                                                              ZLX          ZLX Switch Control.                                             Selects the output of the ZLX switch.                                   Bits 48-49                                                                              ZSPA         ZSPA Switch Control.                                            Selects the output of the ZSPA switch.                                  Bits 48-50                                                                              AUXIN        Auxiliary Register Input                                                       Control.                                                        Selects data to be strobed into auxiliary                                      register(s).                                                            Bit 49   ZADSP        ZADSP Switch Control.                                           Selects the output of ZADSP switch.                                     Bits 50-52                                                                              ZSC          ZSC Switch Control.                                             Selects the output of ZSC switch.                                       Bits 50-52                                                                              ZRSPA        ZRSPA Switch Control.                                           Selects the output of ZRSPA switch.                                     Bits 50-5                                                                               ZAAU         ZAAU Switch Control.                                     Bit 51   RSIR         RSIR Register Strobe.                                           Strobes the RSIR register as a function of the                                 AUXIN field.                                                            Bit 53   RDW          R1DW, R2DW Register                                                            Strobe.                                                         Strobes the R1DW or R2DW register as a function                                of the RDESC register.                                                  Bits 53-54                                                                              ZLNA         ZLNA Switch Control.                                            Selects output of ZLNA switch.                                          Bits 54-57                                                                              CONTF        Miscellaneous Flip-Flop                                                        Control.                                                        Selects one of four groups of control flip-flops                               to be set or reset by the control constant                                     field (CCM). The flip-flops include those of                                   blocks 704-104 and 704-110.                                             Bits 55-56                                                                              ZLNB         ZLNB Switch Control.                                            Selects the output of ZLNB switch.                                      Bist 55-56                                                                              ZSPA(2)      ZSPA Switch, RSPA Register                                        Type A=2)    Control.                                                        Selects ZSPA switch output and strobes RSPA                                    register.                                                               Bits 57-58                                                                              ZPC          ZPC Switch Control.                                             Selects the output of ZPC switch.                                       Bits 59-62                                                                               ZXP         ZXP Switch, RXP Register                                                       Bank Control.                                                   Selects ZXP switch output and the RXP register                                 into which it will be written.                                          Bits 59-63                                                                              ZLN(1)       ZLN Switch, RLN Register                                          (Type A=1)   Bank Control.                                                   Selects ZLN switch output and the RLN register                                 into which it will be written.                                          Bits 59-60                                                                              ZPA          ZPA Switch Control.                                             Selects the output of ZPA switch.                                              00 = RP0                                                                        .                                                                              .                                                                              .                                                                              .                                                                             11 = RP3                                                                Bits 61-62                                                                              ZPB          ZPB Switch Control.                                             Selects the output of ZPB switch.                                              00 = RP0                                                                        .                                                                              .                                                                              .                                                                              .                                                                             11 = RP3                                                                Bits 63-64                                                                              ZXPL         ZXPL Switch Control.                                            (Type A=0)                                                                     Selects the output of ZXPL switch.                                             00 = RXPA                                                                       .                                                                              .                                                                              .                                                                              .                                                                             11 = RXPD                                                               Bit 63   ZLN(2)       ZLN Switch, RLN Register                                          (Type A=2)   Bank Control.                                                   Selects ZLN switch output and the RLN register                                 into which it will be written.                                          Bits 63-66                                                                              RDIN         RDI In Control.                                                 Selects the data to be strobed into the RDI                                    register and selects one of the modification                                   control fields (MF.sub.1 -MF.sub.3, TAG) of an instruc-                        tion word. RDI strobe may also be controlled                                   by the MISCREG field.                                                   Bit 64   ZXPL(1)      ZXPL Switch Control.                                            (Type A=1)                                                                     Selects the output of ZXPL switch.                                      Bits 64-68                                                                              ZRPAC        ZRPA Switch, ZRPC Switch,                                         (Type A=2)   RPO-3 Register Bank Control.                                    Selects ZRPC and ZRPA switch outputs and the                                   RPO-3 register into which the ZRPA output will                                 be written.                                                             Bits 65-66                                                                              ZXPR         ZXPR Switch Control.                                            Type A=0)                                                                      Selects the output of ZXPR switch.                                      Bits 65-66                                                                              ZXP(1)       ZXP Switch, RXP Register                                          (Type A=1)   Bank Control.                                                   Selects ZXP switch output and the RXP register                                 into which it will be written.                                          Bits 67-68                                                                              ZPD          ZPD Switch Control.                                             (Type A=0)                                                                     Selects the output of ZPD switch.                                       Bit 67   ZRPAC(4)     ZRPA Switch, ZRPC Switch,                                         (Type A=4)   RPO-3 Register Bank Control.                                    Selects CP4 from ZRPA switch and strobes the                                   RP1 register.                                                            Bit 67  TYPD         Type D Flag.                                                    Type D Flag which indicates type D overlayed                                   fields.                                                                 Bit 68   ZRPB(4)      ZRPB Switch, RP4-7 Register                                       (Type A=4)   Bank Control.                                                   Selects 0 from ZRPB switch and strobes the                                     RP4 register.                                                           Bits 68-71                                                                              MEM          Cache Memory Control.                                           Selects the cache operation in conjunction                                     with the SZ control.                                                           0)  0000   No operation                                                            .                                                                              .                                                                              .                                                                              .                                                                          15) 1111   Write Remote                                                 Bits 68-70                                                                              IBUF         IBUF Read Control.                                              Selects the destination of IBUF data when                                      reading IBUF.                                                           Bits 69-73                                                                              AXP          ZXPA Switch, ZXPB Switch,                                         (Type A=0)   AXP Adder, ZAXP Switch,                                                        RE Register Control.                                            Selects ZXPA and ZXPB switch outputs, the AXP                                  adder function applied to them, and the ZAXP                                   switch output. Also strobes the RE register.                            Bits 69-73                                                                              ZRPB         ZRPB Switch, RP4-7 Register                                       (Type A=1)   Bank Control.                                                   Selects ZRPB switch output and the RP4-7                                       register into which it will be written.                                 Bits 69-71                                                                              ZRPAC-3      ZRPA Switch, ZRPC Switch,                                         (Type A=3)   RP0-3 Register Bank Control.                                    Selects ZRPC and ZRPA switch outputs and the                                   RP0-3 register into which the ZRPA output will                                 be written.                                                             Bits 72-74                                                                              ZRPB(3)      ZRPB Switch, RP4-7 Register                                       (Type A=3)   Bank Control.                                                   Selects ZRPB switch output and the RP4-7                                       register into which it will be written.                                 Bits 72-73                                                                              SZ           Size/Zone Cache Control.                                        Controls cache operations in conjunction with                                  the MEM control field.                                                  Bits 74-78                                                                              ZRPB(0)      ZRPB Switch, RP4-7 Register                                       (Type A=0)   Bank Control.                                                   Selects ZRP switch output and the RP4-7 regis-                                 ter into which it will be written.                                      Bits 74-78                                                                              AL           ZALA Switch, ZALB Switch,                                         (Type A=1)   AL Adder Control.                                               Selects ZALA and ZALB switch outputs and the                                   AL adder function applied to them.                                      Bit 74   TYPE         Type E Flag.                                                    Type E flag which indicates the type Eover- -layed fields.              Bits 75-77                                                                              ZXP (3)      ZXP Switch, RXP Register                                          (Type A=3)   Bank Control.                                                   Selects ZXP switch output and the RXP register                                 into which it will be written.                                          Bits 75-78                                                                              MISCREG      Miscellaneous REgister                                                         Control.                                                        Selects various operations on miscellaneous                                    registers (e.g. RBIR, RDI, RLEN, RSPP).                                 Bits 75-78                                                                              ZDO          ZDO Switch Control.                                             Selects the output of the ZDO switch.                                   Bit 78   ZIZN         ZIZN Switch Control.                                            Selects the output of ZIZN switch.                                      Bits 79-83                                                                              AP           ZAPA Switch, ZAPB Switch,                                                      AP Adder Control.                                               Selects ZAPA and ZAPB switch output and the                                    AP adder function applied to them.                                      Bits 79-81                                                                              ZLN (3)      ZLN Switch, RLN Register                                          (Type A=3    Bank Control.                                                   Selects ZLN switch outputand the RLN register                                  into which it will be written.                                          Bits 79-83                                                                              ZLN (4)      ZLN Switch, RLN register                                          (Type A=4)   Bank Control.                                                   Selects ZLN output and the RLN register into                                   which it will bwe written.                                              Bits 80-81                                                                              RAAU         RAAU/RE Register Strobe.                                        Selects the data to be strobed into the RAAU                                   and RE registers by controlling several                                        switches and adders in the unit 722.                                    Bits 82-83                                                                              AP (3)       ZAPA Switch, ZAPB Switch,                                         (Type A= 3)  AP Adder Control.                                               Selects ZAPA and ZAPB switchoutputs and the                                    AP adder function applied to them.                                      Bit 84   ZRSC         ZRSC Switch Control.                                              (Type A=0)                                                                   Selects the output of ZRSC Switch.                                      Bits 85-86                                                                              N/A                                                                   Bit 86   RLEN         RLEN Strobe Control.                                            (Type A=3)                                                                     RLEN strobes are also controlled by hardware                                   or by the MISCREG field.                                                Bit 87   FMT          Format Flag.                                                    Indicates the type of format.                                           Bits 88-89                                                                              TYPF                                                                         Indicates the type of overlayed fields.                                        00   =     Scratchpad Address                                                  01   =     Character Unit Control                                              10   =     Multiply/Divide Control                                             11   =     N/A                                                          Bit 90   RFU          Reserved dor Future Use.                                 Bits 90-93                                                                              CHROP        Character Unit Op Code.                                         Selects main operation to be performed by                                      Character Unit and the interpretation to be                                    given to the CHSUROP field.                                                      0)     0000      No operation                                                  1)     0001      Load Data                                                     2)     0010      MOP Execute                                                   3)     0011      Compare Single                                                4)     0100      Compare Double                                                5)     0101      Load Register                                                 6)     0110      Update CN                                                     7)     0111      Undefined                                                     8)     1000      Set RCH Operation A                                           9)     1001      Set RTF1                                                      10)    1010      Set RTF2                                                      11)    1011      Set RTF3                                                      12)    1100      Set RCN1                                                      13)    1101      Set RCN2                                                      14)    1110      Set Edit Flags                                                . 15)  1111      CH Unit Clear                                        Bit 90   RCH              RCH register Strobe.                                        Strobes the OP1 RCH register.                                           Bit 90   RFU          Reserved for Future Use.                                 Bits 91-97                                                                              SPA          Scratchpad Address.                                             Contains the address that may be used to                                       address the EU scratchpad.                                              Bits 91-93                                                                              N/A                                                                   Bits 94-97                                                                              CHSUBOP      Character Unit Sub-Op Code.                                     Selects the detailed function pf the Character                                 Unit or it may contain a constant. The inter-                                  pretation of this field is a function of the                                   CHROP control as shown below.                                                  CHROP = 000 No Operation                                                       CHSUBOP.sub.0-3                                                                   XXXX        No interpretation                                                 CHROP = 0001 Load Data Operation                                               CHSUBOP.sub.0-1                                                                             (Suboperation)                                                     00          OP1 Load by CN1 and TF1                                            01          OP1 Load in Reverse by CN1                                                     and TF1                                                            10          OP2 Load by CN2 and TF2 and                                                    Test Character                                                     11          Load Sign                                                         CHSUBOP.sub.2-3                                                                             (Fill Control)                                                     1X          Fill character loaded to ZCU                                       X1          Fill character loaded to ZCV                                      CHROP = 0010 MOP ExecuteOperation                                              CHSUBOP.sub.0-1                                                                             (Suboperation)                                           10 00    MOP set by CN2                                                                  01          MOP Execute                                                        10          Undefined                                                          11          Undefined                                                         CHSUBOP.sub.2-3                                                                 XX          No interpretation                                                 CHROP = 0101 Load Register Operation                                           CHSUBOP.sub.2-3                                                                             (Selects output of ZOC switch)                                    CHROP = 1011 Set RTF3 Operation                                                CHCUBOP.sub.0-1                                                                             (Selects data to be inspected                                                  for 00, indicating a 9-bit                                                     character.                                                        CHSUBOP.sub.2-3                                                                             (Constant Field)                                                  CHROP = 1110 Set Edit Flags Operation                                          CHSUBOP.sub.0-3 (Constant selecting flags to be                                             set)                                                               1XXX        Set ES (End suppression)                                           X1XX        Set SN (sign)                                                      XX1X        Set Z (zero) -  XXX1 Set BZ (Blank When Zero).           Bits 94-97                                                                              RFU          Reserved for Future Use.                                 Bits 97-97                                                                              N/A                                                                   Bit 98   TYPG         TYPE G FLAG.                                                    Indicates the type of overlayed fields.                                         0 = BRADRU field                                                               1 = IND6 field                                                          Bit 99  GO           State of Conditional Branch                                                    Test.                                                    Bits 99-106                                                                             BRADRU       Branch Address Upper.                                    Bits 99-106                                                                             IND6FLD      Indicator Control.                                                Selects an indicator.                                                 Bits 99-106                                                                             Bit 99= 0 specifies a change indicators                                        instruction.                                                                   Bit 99 = 1 specifies a set/reset indicators                                    instruction (set or reset indicated by X bit                                   0 to 1 respectively.                                                         Bits 100-104                                                                             =1         106=1                                                     0000                                                                           .                                                                              .                                                                              .                                                                              .                                                                              1100X     Exhaust 1  Exhaust 2                                                 1101X     Exhaust 3  N/A                                                       1110X     Exhaust1   Exhaust 2                                                           Eff.       Eff.                                               Bits 107-112                                                                            BRADRL       BRANCH ADDRESS LOWER.                                           Contains lower portion of an ECS address used                                  for branching.                                                          Bit 113  EXIT         Selection of Switch                                                            Control.                                                        Selection of Exit indicates end of micropro-                                   gram.                                                                   Bits 114-116                                                                            ZCSBRA       ZCSBRA Switch Control.                                          Defines the position to be selected in a Con-                                  trol Store Branch Address Switch.                                       Bits 117-118                                                                            N/A                                                                   Bits 119-123 INDGRP                                                                     Conditional Branch Indicator                                                                Group Control.                                                  THE FIRST TWO BITS (119-120 select the "group"                                 of microprogram indicators. The last three                                     bits (121-123 select the "set" of indicators                                   within each "group".                                                    Bit 124  TYPH         Type H field.                                                   Indicates the type H overlayed fields.                                          0 = INDMSKU                                                                    1 = VCTR field                                                         Bits 125-128                                                                            INDMSKU      Conditional Branch Indicator                                                   Mask Upper.                                                     Contains the upper 4 bits of the indicator                                     mask in type H = 0 field.                                               Bits 125-129                                                                            VCTR         Vector Select.                                                  Selects the branching vectors to be strobed                                    into the RVB0, RVB1 and RVB2 registers. The                                    most significant bit (125) determines which                                    of two groups 0 oir 1, 2 or 3 and 4 or 5 will                                  be strobed into the RVB0, RVB1 and RVB2                                        registers respectively. The remaining 3 bits                                   select the vector within each group.                                    Bits 129-132                                                                            INDMSKL      Conditional Branch Indicator                                                   Mask Lower.                                                     Contains the lower 4 bits of the indicator                                     mask.                                                                   Bits 133-135                                                                            N/A                                                                   Bits 136-139                                                                            CNSTU        Constant Upper.                                                 Contains the upper 4 bits of the constant                                      field.                                                                  Bits 140-143                                                                            CNSTL        Constant Lower.                                                  Contains the lower 4 bits of the constant                                     field.                                                                  ______________________________________                                    

CONTROL LOGIC UNIT 704-1

This unit includes the sequence decode logic circuits 704-100 as mentioned whose outputs feed a plurality of I cycle control state flip-flops of block 704-102. These flip-flops in response to signals from the circuits 704-100 as well as microinstruction signals from register 701-4 (DEMR038-40 which correspond to the mem address field MEMADR of FIG. 6b) generate the various required I cycle control states required for the execution of program instructions. It is assumed that block 704-102 also includes gate circuits which generate register hold signals [HOLDE00 which are distributed throughout the processor 700.

As seen from FIG. 3c, the I cycle control state flip-flops receive control input signals via control lines including a line CPSTOP00 from cache unit 750. As explained herein, the state of the CPSTOP00 line determines whether processor operation continues in that when the line is forced to a binary ZERO, the hold or enabling signals for the I cycle control state flip-flops and other storage registers are also forced to ZEROS. The hold signals corresponding to signals [HOLDI00 and [HOLDE00 operate to hold or freeze the state of the processor 700. Since no incrementing of the control store address can take, the ECS control store reads out the same microinstruction word. The signals [HOLDI and [HOLDE are set in accordance with the following Boolean expressions: [HOLDI=CACHE HOLD+TERMB (DREQ-IF-DIR)+HOLD REL wherein the state of signal CACHE HOLD corresponds to the state of signal CPSTOP, the states of signals TERMB (DREQ-IF-DIR) are binary ONES during control state EPOA when the cache command specifies an I fetch or direct operation and the signal HOLD REL is a binary ONE until switched to a binary ZERO by the generation of a microprogram release signal; and [HOLD E=[HOLD I.

In accordance with the teachings of the present invention, each of the instructions which comprise the repertoire of the preferred embodiment of the present invention are assigned one of a number of control sequence codes (CCSS) as follows which enable efficient instruction cycle processing. These different classes of hardwired sequences are established to permit the kind of performance desired for the execution of the entire repertoire of instructions listed in Appendix A. The hardwired sequence selected for each instruction is chosen to provide the particular type of performance required for efficient pipeline operation.

The instructions are designated by mnemonics which are listed in an instruction index included in an appendix A. A number of the instructions are described in the publication "Series 60 (Level 66)/6000 MACRO Assembler Program (GMAP)"by Honeywell Information Systems Inc., copyright 1977, order number DD08B, Rev. 0.

    __________________________________________________________________________     CCS-S                                                                              SEQUENCE     INSTRUCTION TYPES                                             __________________________________________________________________________     000000                                                                             LD-SGL      LDA, LDQ, LCA, LCQ, ADA, ADQ, ADLA,                                            ADLQ, AWCA, AWCQ, SWCA, SWCQ, CMPA,                                            CMPQ, CANA, CANQ, ANA, ANQ, ORA,                                               ORQ, ERA, ERQ, SBA, SBQ, SBLA,                                                 SBLQ, LDE, SZN, FSZN, LXLN, LDI                                000001                                                                             LD-SGL-DEL  FLD, CNAA, CNAQ, ADE                                           000010                                                                             LD-SGL-ESC  MPY, MPF, DIV. DVF, CWL, CMG, CMK,                                             FAD, UFA, FSB, UFS, FMP, UFM, FDV,                                             FDI, LDT, FCMP, FCMG, CCD, ADL,                                                XEC, CIOC, LPDBR, LDDSA, LDO, LDPn,                                            LDEAn, PAS, LARn, AARn, NAARn, LDWS                            000011                                                                             LD/STR-SGL-ESC                                                                             ASA, ASQ, AOS, SSA, SSQ, ANSA,                                                 ANSQ, ORSA, ORSQ, ERSA, ERSQ,                                                  ARAn, ARNn, SARn.                                              000100                                                                             LD-HWU      LDXn, LCXn, ADXn, ADLXn, SBXn,                                                 SBLXn, ANXn, ORXn, ERXn, CMPXn                                 000101                                                                             LD-HWU-DEL  CNAXn                                                          000110                                                                             LD-HWU-ESC  LBAR, LBER, LMBA, LMBB                                         000111                                                                             LD/STR-HWU-ESC                                                                             ASXn, SSXn, ANSXn, ORSXn, ERSXn                                001001                                                                             LD-DBL      LDAQ, LCAQ, ADAQ, ADLAQ, SBAQ,                                                 SBLAQ, ANAQ, ORAQ,, ERAQ, CMPAQ,                                               CANAQ, DFLD                                                    001010                                                                             LD-DBL-ESC  CNAAQ, XED, LDSS, LDAS, LDPS,                                                  LDDSD, DFSB, DUFS, DFMP, DUFM,                                                 DFDV,DFDI, DFCMP, DFCMG, DFAD,                                                 DUFA, QFLD, QFAD, QFSB, QFMP, QSMP,                            010000                                                                             STR-SGL     STA, STQ                                                       010001                                                                             STR-HWU     STXn                                                           010010                                                                             STR-DBL     STAQ                                                           010100                                                                             RD-CLR                                                                     011000                                                                             EFF-ADR     EAA, EAQ, EAXn, NEG                                            011010                                                                             EFF-ADR-ESC ARS, QRS, LRS, ALS, QLS, LLS, ARL,                                             QRL, ERL, ALR, LLR, QLR, GTB, NEGL                             100000                                                                             TRF         TRA, TZE, TNZ, TMI, TPL, TRC, TNC,                                             TOV, TEO, TEU, TTF, TRTN, TRTF, TTN,                                           TMOZ, TPNZ                                                     100100                                                                             ESC         RCCL, LCCL, RPT, RPD, RPL, STCA,                                               STCQ, STBA, STBQ, MME, DRL, ILLOC,                                             CCAC, AWD, SWD, A9BD, A4BD, A6BD,                                              ABD, S9BD, S4BD, S6BD, SBD, CAMP,                                              RPN, RIMR, SFR, LLUF, LIMR, RRES,                                              HALT, SDRn, EPAT.                                              100101                                                                             ESC-LD      MLDA, MLDQ, MLDAQ                                              100110                                                                             ESC-ST      MSTA, MSTQ, MSTAQ                                              101000                                                                             NO-OP       NOP                                                            101001                                                                             TSXN        TSXN                                                           101010                                                                             ESC-EA      LREG, SREG, STC1, STC2, FSTR, DFSTR,                                           STE, SBAR, TSS, RET, SPL, LPL,                                                 STI, SBER, SMBA, SMBB, SAREG, SXLn,                                            EPAT, EPPRn, CLIMB, STWS, STPn,                                                LAREG, QFSTR, LDDn, FST, DFST, FRD,                                            DFRD, FNEG, FNO, STDn, LDAC, LDQC,                                             SZNC, DIS                                                      101100                                                                             DEL-STR-SGL STT, STZ, SPDBR, STPDW, STPTW,                                                 STDSA, STO                                                     101101                                                                             DEL-STR-DBL STSS, STDSD, STTA, STTD, STPS, STAS,                                           SDZn, QFST                                                     110000                                                                             BIT         CSL, CSR, SZTL, SZTR, CMPB                                     110001                                                                             MTM-MTR     MTM, MTR                                                       110011                                                                             MRL         MRL                                                            110100                                                                             TCT         TCT                                                            110101                                                                             TCTR        TCTR                                                           110110                                                                             SCAN-FWD    SCM, SCD                                                       110111                                                                             SCAN-REV    SCMR, SCDR                                                     111000                                                                             NUM2        MVN, MVNX, CMPN, CMPNX, AD2D, AD2DX,                                           SB2D, SB2DX, DV2D, DV2DX, MP2D,                                                MP2DX                                                          111001                                                                             MVT         MVT                                                            111010                                                                             CONV        BTD, DTB                                                       111011                                                                             MLR         MLR                                                            111100                                                                             NUM3        AD3D, AD3DX, SB3D, SB3DX, MP3D,                                                MP3DX, DV3D, DV3DX                                             111101                                                                             EDIT        MVE, MVNE, MVNEX                                               111110                                                                             CMPC        CMPC                                                           111111                                                                             CMPCT       CMPCT                                                          __________________________________________________________________________

The different assignable hardwired sequences operate in the following manner.

HARDWIRED SEQUENCES LD-SGL SEQ

This hardwired sequence causes the control unit to generate the effective address during a FPOA cycle and to cause the cache unit to execute a read single memory cycle of operation. When indirect addressing is specified, control is transferred to an address preparation microprogram routine. The requested data is loaded into the RDI register at the completion of the cache cycle and is then available for use during the execution cycle.

LD-SGL-DEL SEQ

This 2T hardwired sequence is the same as LD-SGL except that a 1T delay state is entered after the FPOA cycle (FPOA→FDEL→FPOA-NEXT).

LD-SGL-ESC SEQ

Same as LD-SGL sequence except the pipeline is stopped after the current FPOA cycle is completed (escape state is entered).

LD-HWU SEQ

Same as LD-SGL sequence except that bits 00-17 of RDI register are loaded from the cache unit. Memory bits 00-17 and zeros are loaded into RDI₁₈₋₃₅.

LD-HWU-DEL

This 2T hardwired sequence is the same as the LD-HWU sequence except a 1T delay state is entered after state FPOA. The sequence is FPOA→FDEL→FPOA-NEXT.

LD-HWU-ESC

This sequence is the same as the LD-HWU sequence except the pipeline is stopped after the completion of the current FPOA cycle.

LD/STR-SGL-ESC

This sequence is the same as the LD-SGL-ESC sequence except that in addition to normal read checks, a write check is also performed. This sequence is used for "READ-ALTER-REWRITE" types of operation.

LD/STR-HWU-ESC

This sequence is the same as LD/STR-SGL-ESC sequence except that bits 00-17 of the RDI register are loaded from the cache unit memory bits 00-17 and zeros are loaded in RDI₁₈₋₃₅.

LD-DBL SEQ

This sequence causes the control unit to generate the effective address during a FPOA cycle and causes the cache unit to execute a read double memory cycle of operation. The requested data is returned to the RDI register on two consecutive cycles.

LD-DBL-ESC SEQ

This sequence is the same as the LD-DBL sequence except the escape state is entered after the current FPOA cycle is completed.

STR-SGL SEQ

This 2T sequence (FPOA→FSTR) causes the control unit to generate an effective address and causes the cache unit to execute a write single memory cycle (FPOA) of operation. During the second cycle (FSTR) the register to be stored (as selected by the contents of the RRDX-A register) is transferred to the RADO register as follows ZX→ZDO→ZRESB→RADO.

STR-HWU SEQ

This sequence is the same as the STR-SGL sequence except that the cache unit causes a change only in bits 00-17 of a memory location.

STR-DBL SEQ

This 3T sequence (FPOA→FSTR-DBL→FSTR) causes the control unit to generate an effective address and causes the cache unit to execute a write double memory cycle (FPOA control state) of operation. During the second and third cycles the EVEN and ODD data words (as selected by the contents of the RRDX-A register) are sent to the cache unit.

RD-CLR SEQ

This sequence is the same as the LD-SGL sequence except the cache unit causes the memory location to be read and also cleared.

EFF-ADR SEQ

This sequence causes the control unit to load bits 00-17 of the RDI register with an effective address that is generated during a FPOA cycle while bits 18-35 of the RDI register are loaded with zeros.

EFF-ADR-ESC SEQ

This sequence is the same as the EFF-ADR sequence except the pipeline is stopped after the FPOA cycle (Escape state is entered).

TRF SEQ

This sequence causes the control unit to request two four word blocks of instructions (during FPOA and FTRF control states) for the instruction buffer in preparation for a transfer of control or any branch operation.

ESC SEQ

This sequence causes the pipeline to be stopped after the FPOA cycle. No memory cycles are initiated and there is no address preparation performed.

ESC-LD & ESC-STR SEQS

These sequences are the same as ESC and are used for executing testing operations.

ESC-EA SEQ

This sequence causes the control unit to load a temporary register with an address pointer generated during the FPOA cycle. The pipeline is stopped after FPOA.

DEL-STR-SGL SEQ

This 3T sequence (FPOA-FDEL-FESC) causes the control unit to generate an effective address during state FPOA and then switch to a second FDEL state. This allows the cache unit an extra cycle to fetch the data to be stored. At the completion of FDEL, the cache unit is caused to initiate a write single memory cycle of operation and the hardware switches to FESC state. The data to be written is transferred to the RADO register under microprogram.

DEL-STR-DBL SEQ

This sequence is the same as DEL-STR-SGL except the sequence is 3T. The sequence is FPOA→FDEL→FESC. A write double memory cycle is initiated during state FDEL. Data is transferred to the RADO register on the cycles following state FDEL under microprogram control.

EDIT SEQ (EIS)

This sequence is FPOA-FPOP1-FPOP2 followed by FPOP3. There is an escape to microprogram control which following the setting up of registers, tables, etc. required for processing edit operands signals the hardware control circuits to enter state FPOP3.

The remaining EIS sequences can be considered as having states similar to that of the EDIT sequence.

TSXn

This sequence causes the processor 700 to compute the effective address and update the instruction counter. During a second cycle (FTSX1), the updated instruction counter is loaded into the RDI register for subsequent transfer to the specified index register. The computed effective address is loaded into TEAO and the processor 700 transfers control to that location (FPIINIT).

The hardwired control states used during I cycle processing in accordance with the present invention and a brief description of the operations performed during such control states or cycles are as follows.

    ______________________________________                                         I CYCLE CONTROL                                                                STATE/CYCLE    DESCRIPTION                                                     ______________________________________                                         FPOA           The FPOA Prepare Operand state is                                              the starting control state for all                                             instructions. During FPOA, an                                                  address is calculated and the op-                                              code is translated via the CCS                                                 control store to control further                                               actions.                                                        FPOP           The FPOP Prepare Operand Pointer                                               state is used to process EIS in-                                               struction descriptors.                                          FSTR           The FSTR Store state is used to                                                transfer "store" data into the                                                 RADO register in the case of in-                                               structions requiring sequences, and                                            to transfer the second (odd) word                                              of double precision data to the                                                RADO register in the case of in-                                               structions requiring store double                                              sequences.                                                      FSTR-DBL       The FSTR-DBL Store Double state is                                             used to transfer the first (even)                                              word of double precision data to                                               the RADO register for those in-                                                structions requiring store double                                              sequences.                                                      FESC           The FESC Escape state is used to                                               provide a variable delay to the                                                I-Process pipeline. During state                                               FESC, the ESC control store has                                                complete control over the processor                                            700, and determines when to restart                                            the I-Process pipeline.                                         FDEL           Thw FDEL Delay state provides a                                                1T delay to the I-Process pipeline.                             FWF-IND        The FWF-IND Wait for Indirect Word                                             state provides the control to                                                  transfer signals on the ZDI lines                                              into the RSIR register.                                         FTRF           The FTRF Transfer state is used to                                             request that the cache unit fetch a                                            second block of instructions for                                               loading into the I Buffer and to                                               strobe a first instruction for a                                               new instruction stream into the                                                processor 700 RBIR register.                                    FTRF-NG        The FTRF-NG Transfer No Go state                                               is used to reload the I Buffer                                                 address registers with the old in-                                             struction stream address.                                       FPIM-1         The FPIM-1 Prepare Instruction                                                 Address for I Buffer Maintenance                                               Type 1 state is entered when the                                               I Buffer runs out of instructions.                                             During the FPIM-1 state, a block                                               of instructions is requested for                                               the I Buffer. Also, during the                                                 FPIM-1 state, a processor-hold                                                 condition occurs when the cache                                                unit signals a Cache-Miss condi-                                               tion.                                                           FPIM-2         The FPIM-2 Prepare Instruction                                                 Address for I Buffer Maintenance                                               Type 2 state enables a second                                                  block of instructions to be re-                                                quested for the I Buffer. Dur-                                                 ing the FPIM-2 state, there is no-                                             processor-hold condition generated                                             when the cache unit signals a Cache-                                           Miss condition. Also, during state                                             FPIM-2, the next instruction is                                                strobbed into the processor's                                                  RBIR register.                                                  FPI-INIT       The FPI-INIT Prepare Instruction                                               Address for I Buffer Initialize                                                state is used to reload the I                                                  Buffer after a transfer (store                                                 compare) or after a Type 3 re-                                                 start.                                                          FWF-IBUF       The FWF-IBUF Wait for I Buffer                                                 Ready state is entered when an                                                 instruction is needed from the I                                               Buffer, and the I Buffer is in a                                               not ready condition.                                            FPIM-EIS       The FPIM-EIS Prepare Instruction                                               Address for I Buffer Maintenance                                               EIS state is entered following                                                 the FPOA cycle of an EIS multi-                                                word instruction whenever the I                                                Buffer does not contain enough                                                 descriptors to complete the processing                                         of the instruction.                                             FWF-DESC       The FWF-DESC Wait for Descriptor                                               state is entered when a descriptor                                             is needed from the I Buffer, and                                               the I Buffer is in a not ready                                                 condition.                                                      FIDESC         The FIDESC Indirect to Descriptor                                              state is the control state used to                                             process EIS indirect descriptors.                               FWF-IDESC      The FWF-IDESC Wait for Indirect                                                Descriptor control state provides                                              the control to transfer the cache                                              word applied to the ZDI lines to                                               the RSIR register 704-154.                                      FIT-I          The FIT-I Indirect and Tally Indirect                                          control state is used to process                                               non-EIS descriptors specifying in-                                             direct and tally indirect address                                              modifications.                                                  FIRT           The FIRT Indirect and Register Test                                            control state is entered during                                                the processing of non-EIS des-                                                 criptors specifying indirect and                                               register address modifications to                                              determine whether the processing                                               of that type of address modification                                           is completed.                                                   FTSX1          Thw FTSX1 Transfer and Set Index                                               control state is used to transfer                                              the updated contents of the instruc-                                           tion counter to the RDI register                                               in the case of transfer and set                                                index instructions.                                             ______________________________________                                    

As seen from FIG. 3c, signals corresponding to the I cycle control states are applied as inputs to a plurality of control flip-flops of block 704-104, decoder circuits of block 704-106, a number of control logic circuits of block 704-108 and to a plurality of control flag indicator flip-flops of block 704-110. It is also seen that the various indicator flip-flops of block 704-110 also receive microinstruction input signals via lines MEMD054-57 from execution control unit 701-4.

As seen from FIG. 3d, signals generated by the hardware control logic circuits 704-108 fall into one of three groups as a function of the units whose operations are being controlled. That is, the groups are instruction buffer control, hardware control and hardware memory control.

In each case, each group of signals are ored together with equivalent signals generated by other sources and then decoded. The other sources correspond to fields within the two different formats of the microinstruction word of FIG. 6a which are loaded into RCSR register 704-112 from the ECS output register 701-4.

One field corresponds to bits 32-83 of one format (large CU) and another field (short CU) corresponds to bits 32-41 of another format. These fields are decoded by a decoder 704-114 into the sets of bits indicated and combined within the decoders 704-116, 704-124, 704-126 and 704-128 as shown. Further decoding is done by the circuits of blocks 704-118, 704-135 and 704-120. The results of decoding such fields are either distributed throughout processor 700 or are stored in an RMEM register 704-130, an RSZ flip-flop 704-132, an FREQDIR flip-flop 704-136 and an FREQCAC flip-flop 704-134.

Additional decoding of the large and short CU fields and signals from the I cycle state circuits of block 704-112 is done via a decoder 704-106 and 704-107. The decoder 704-106 generates control signals for loading different ones of the registers and for enabling various multiplexer/selector switches within the processor 700. The decoder 704-107 operates to generate signals for setting and resetting a pair (RBASB) of base pointer B flip-flops 704-144. Other combinations of these signals are used to set and reset the descriptor number flip-flops of blocks 704-140 and 704-142.

As seen from FIG. 3c, the decoder 704-116 receives a control signal [EXH00 generated by the decoder circuits of block 704-117. These circuits receive signals from the RDESC register 704-140 and signals from the exhaust flip-flops of block 701-1. In accordance with the states of these signals, the circuits force signal [EXH000 to a binary ZERO to inhibit the generation of a cache memory command upon the occurrence of an exhaust condition. The signal [EXH000 is generated in accordance with the following Boolean expression:

    [EXH000=DESCO·FE11+DESC1·FE2+DESC2·FE3.

the flip-flop FNUM is normally set in response to the CCS-OP field of the microinstruction word. When set to a binary ONE, this indicates that the descriptor being processed is a numeric type.

The different flip-flops of block 704-104 will now be discussed in greater detail. In greater detail, the flip-flop FCHAR provides certain changes in the control of address generation. When the FCHAR flip-flop is set to a binary ONE during the processing of a load type instruction specifying character modification, then the contents of the RDI register is not changed under hardware control. This allows the RDI register to be loaded with data under microprogram control prior to starting the pipeline. Also, if the FCHAR flip-flop is set to a binary ONE during a store type instruction specifying character modification, then the execution address for this instruction is modified under hardware control to point to a unique address of the microinstruction sequence in the ECS control store that is to process this type of instruction.

The flip-flop FDT-FOUR provides additional control on the readout of the address register (ZAR₀₋₁₉) of block 704-304. Flip-flop FADR-WD provides additional control for the ZDO switch 704-340. When this flip-flop is set to a binary ONE, then the ZAR position of the ZDO switch is forced to select a word address. The flip-flop FADR-B provides additional control for the ZDO multiplexer switch. When set to a ONE, then the ZAR position of the ZDO switch is forced to select a byte address. The flip-flop FNUM is normally set in response to the CCS-OP field of the microinstruction word. When set to a binary ONE, this indicates that the descriptor being processed is a numeric type. The flip-flop FIG-LEN provides additional control over the loading of registers within the unit 722 (length registers) and over memory operations. When set to a binary ONE, the RXP and RLN registers within unit 722 are not loaded from the RSIR register 704-154 during control states FPOP.

The FINH-ADR flip-flop inhibits the operation of the address preparation unit 704-3. When set to a binary ONE, an address cycle (FPOA/FPOP) consists of adding the contents of a temporary effective address register REA-T+ZERO. The register REA-T will have been loaded with the address prior to doing a FPOA/FPOP cycle. The FABS flip-flop enables the generation of absolute addresses. When set to a binary ONE, a 24-bit absolute address is used. As concerns the flag or indicator flip-flops of block 704-110, flip-flop FID when set to a binary ONE provides an indication that indirect address modification during an instruction is required on the descriptor loaded into the RSIR register.

The FRL flip-flop when set to a binary ONE indicates that the length is specified in a register associated with the instruction loaded into various instruction registers. The three flip-flops FINDA, FINDB and FINDC provide indications used in processing memory type instructions. Flip-flop FINDA is set to a binary ONE when length is specified in a register or when flip-flop FAFI is set to a ONE. Flip-flop FINDB is set to a binary ONE when the descriptor does not include nine bit characters. The flip-flop FINDC is set to a binary ONE when the descriptor does include six bit characters.

The FAFI flip-flop is set to a binary ONE when the processor circuits detect that indicator bit 30 of IR register 701-41 was set to a binary ONE during the execution of an EIS instruction indicative of a mid instruction interrupt (required to adjust pointer and length values because of interrupt). The FTRGP, FTNGO and FTRF-TST flip-flops are set to binary ONES in conjunction with transfer type instructions. More specifically, the FTRGP flip-flop provides a microprogram indication of being set to a binary ONE when the processor circuits detect the read out of a transfer type of instruction during the execution of an execute double (XED) or repeat (RPTS) instruction. The FTNGO flip-flop provides a microprogram indication of being set to a binary ONE when the condition of transfer signalled by the execution control unit 701 was transfer NO GO (i.e., transfer did not take place). The FTRF-TST flip-flop of this group indicates when set to a binary ONE that the previous instruction executed by processor 700 was a transfer type instruction and that the current I cycle is to be executed conditioned upon the presence of a transfer GO (TRGO) signal from control unit 701.

Additionally, the circuits of block 704-110 include a number of flip-flops used in performing indirect addressing operations under hardwired control for other than EIS instructions. These include FIR, FIRT, FIRL and FRI flip-flops which are switched to binary ONES as functions of the different types of indirect address modifications required to be performed. For example, the FRI flip-flop signals a register then indirect address modification and is switched to a binary ONE when a register indirect (RI) indicator is a binary ONE. The FIR flip-flop is switched to a binary ONE when an indirect then register (IR) indicator is a binary ONE. This flip-flop signals the beginning of an indirect then register address modification. The FIRL flip-flop is switched to a binary ONE when an indirect then tally indirect (IT-I) indicator is a binary ONE. This flip-flop signals a last indirect operation. Another flip-flop TSX2 provides an indication used in processing transfer and set index instructions while a STR-CPR flip-flop is used during the processing of store instructions.

As seen from FIG. 3c, the outputs from the control flag flip-flops of block 704-110 are applied as inputs to the branch indicator circuits of block 701-1. Also, output signals from the control flag flip-flops are also applied as inputs to the I cycle flip-flops of block 704-102.

Register Section 704-150

As seen from FIG. 3c, the control logic unit 704-1 further includes a register section 704-150. This section contains the basic instruction register (RBIR) 704-152, the secondary instruction register (RSIR) 704-154, a base pointer A register (RBASA) 704-156 used for selecting one of the address registers RAR0 through RAR7 of block 704-304, a read index register A (RRDXA) 704-158 used for selection of index registers included within section 704-5 (not shown) and for selection of outputs from the ZDO multiplexer switch 704-340, a read index A save (RRDXAS) register 704-159, and a descriptor type register (RTYP) 704-160 indicating the type of data characters being pointed to by the descriptor value (e.g. 9-bit, 6-bit, 4-bit). The section 704-150 further includes a 1-bit instruction/EIS descriptor register designated R29 of block 704-162. The state of this bit in conjunction with the contents of the RBAS-A register 704-158 are used to select the particular address register used for address preparation. When register R29 of block 704-162 is set to a binary ZERO, this indicates that none of the address registers of block 704-304 are used during address preparation. The last registers of section 704-150 include the data in register (RDI) of block 704-164 and a read index register B (RRDXB) pointing to registers used by execution unit 714.

As seen in FIG. 3, the RBIR register 704-152 is loaded via a two position switch 740-170 connected to receive signals from the sources indicated (i.e., a switch ZIB-B 704-172 and lines ZDI 0-35). The RSIR register 704-154 similarly receives signals from the ZDI lines and switch 704-172. The RBASA register 704-156 receives signals from the ZDI line 0-2 in addition to a further switch ZBASA of block 704-174. The RRDXA register and RTYP register receive signals from the ZDI lines as well as a switch 704-176 and switch 704-178 as shown. Also, the RRDXA register receives signals from the RRDXAS register 704-159.

The switch 704-172 is a two position switch which receives inputs from the switches ZIB and ZRESB from the cache unit 750 and execution unit 714 respectively. The switch 704-174 is a three input switch which receives two inputs from the execution units 714 and the output of the ZIB switch of cache unit 750.

Switch 704-176 is a four input switch which receives two of its inputs from the execution unit 714 and a single input from cache unit 750. The first position of the ZRDXA switch 704-176 selects the output of a ZRDXM switch 704-185. One position of this switch provides a tag field value from bit positions 5-8, 14-17, and 32-35 of the RBIR register 704-152 and bit positions 32-35 of the RSIR register 704-154 selected from ZIDD switch 704-180 and a two position ZMF switch 740-176.

The second position of switch 704-185 provides a constant value from the output of the ECS output register 704-1 (CCM field 32-34). The signals from the lines ZIDD 27-35 are applied as inputs to control flag flip-flops of block 704-110. The switch 704-178 receives an input from the control store 704-2, an input from cache unit 750 and an input from execution unit 714.

The data input register 704-164 receives a series of input signals from a ZIDD switch 704-180 which connects in series to a ZDIA switch 704-181 whose output provides one input of a further switch 704-182 which directly loads into the RDI register 704-164. The ZDIA switch 704-181 provides a further input to a three input switch 704-183 which receives the other inputs indicated from cache unit 750 and execution unit 714.

The ZIDD switch 704-180 receives an effective address via switch 704-186 from the address preparation unit 704-3 as well as inputs from the RBIR register 704-152, the RSIR register 704-154 and a two position ZMF switch 740-187. The positions 18 through 35 of the REA position of switch 704-180 are derived from the ZDIA switch 704-181 as shown. The ZDIA switch 704-181 receives signals from the ZDI lines 0-35, a constant value generated from the inputs to a first switch position in addition to signals from the output of the ZIDD switch 704-80 and the ZRESB switch in execution unit 714. The switch 704-182 receives the output of the ZDIA switch and signals from the ZDI lines 0-35. The RRDXB register 704-189 is loaded by a three position switch 704-188. The switch receives via a first position signals from a RREG register included in the execution unit, a constant value from control store 701-2 via a second position and signals from the ZIDD switch via a third position.

The section 704-150 further includes a two position switch 704-185 and a scratchpad pointer register 704-186 whose output is used by the AACU 722 to form addresses for access to the scratchpad memory of the EU 714. The first switch position provides a constant value and is selected under hardware control (FPOA·R29). The second switch position applies as an output the contents of the RBASA register 704-156. This position is selected under both hardware and microprogram control (i.e., FPOA·R29 or MISCREG field).

It will be appreciated that the required timing signals for operating section 704 as well as other sections of processor 700 and cache unit 750 are provided by centrally located clock circuits. For example, in the preferred embodiment of FIG. 1, the clock circuits are located within the input/output processor 200. Such clock circuits can be considered as conventional in design and can comprise a crystal controlled oscillator and counter circuits. The timing or clocking signals from such clock circuits are distributed in a conventional manner to the various portions of the system of FIG. 1 for synchronized operation.

ADDRESS PREPARATION UNIT 704-3

The address preparation unit 704-3 includes a number of registers and adders. The registers include a number of base registers (i.e., TBASE0 through TBASEB) of block 704-300 used for storing descriptor values of an instruction, a pair of temporary effective address registers (TEA0, TEA1) and a pair of instruction counters (ICBA, ICBB) included within block 704-302 used for addressing the instruction buffer and eight address registers (RAR0 through RAR7) of 704-304 used during address preparation operations. The unit 704-3 also includes an instruction counter 704-310.

The adders include adder 704-312 used to update instruction counter 704-310 via switches 704-311 and 704-314 and a pair of adders 704-320 and 704-322. The adder 704-322 is used to generate an effective address value which is stored in a register 704-342 applied as an input of the control unit 704-1. The effective address is generated from a number of sources which include ZY switch 704-326 whose output is applied via a number of AND gates of block 704-327, selected address registers of block 704-304 or selected temporary address registers TEA0 and TEA1 of block 704-302 applied via another switch 704-328 or the index address signals ZX0-20 from unit 704-5. Additionally, adder 704-322 is used to update the contents of the instruction counter of the cache instruction buffer.

As seen from FIG. 3d, the outputs from adder 704-322 are also applied as an input to the adder 704-320. The adder 704-320 is used to combine base value stored in any one of the temporary base registers TBASE0 through TBASEB with the address signals ACS0S0-19 from adder 704-322. The resulting bits are applied as an input to a further adder network 704-320 which generates a logical address which is applied to the lines ASFA0-36 via an adder 704-321. This adder sums the operand inputs together with the carry inputs from blocks 704-300 and 704-320. The effective address is used to obtain an absolute address when the system is operated in a paged mode. Since this operation is not pertinent to the present invention, it will not be discussed further herein. For further information regarding such address development, reference may be made to U.S. Pat. No. 3,976,978.

The temporary base registers of block 704-300 are loaded via a switch 704-332. The switch receives an input from the execution unit 714 and the output from block 704-300. The execution unit 714 applies further inputs to the registers of block 704-302 via a switch 704-334 as well as to the address registers of block 704-304. An output multiplexer (ZD0) switch 704-340 enables the selection of the various registers within the address preparation unit 704-3 and unit 704-5 for transfer of their contents to the execution unit 714 via lines ZDO 0-35. Also, the ZDO switch 704-340 enables the contents of various ones of the registers and control flip-flops of unit 704-1 to be read out via a fourth position (ZDO-A). The fifth position enables the states of various indicators within the control store circuits of block 701-1 to be selected for examination.

XAQ REGISTER SECTION 704-5 AND DATA ADDRESS OUTPUT SECTION 704-4 FIGS. 3e AND 3f

The section 704-5 includes the accumulator RA register 704-50, the quotient QA register 704-52 and the temporary index (RTX) register 704-54 utilized by the control logic unit 704-1. Additionally, it includes a group of eight index (X0-7 ) registers included within block 704-51. These registers are loaded via the ZRESA bus in execution unit 714. The selection of the register to be loaded is controlled by the contents of the RRDXB register 704-189. It will be noted from FIG. 3f that selection of outputs from the registers of block 704-51 is controlled by the contents of both the RRDXA and RRDXB registers 704-158 and 704-189 respectively. The contents of program visible registers RA, RQ, X0-7 and RTX are read out to the unit 704-3 via a ZXA2 switch 704-56, a ZXOB switch 704-57 and a ZX switch 704-58. From there, the register contents can be transferred to execution unit 714 or to cache unit 750 via the ZDO switch in unit 704-3.

As seen from FIG. 3f, the output ZXA2 switch 704-56 is applied via an AND gate 704-61 and an OR gate 704-62 in accordance with the contents of RRDA register 704-158.

The selection of outputs from the above mentioned switches are controlled by the contents of the RRDXA register 704-158, the FNUM flip-flop of block 704-104 and the RTYP register 704-160 in addition to bits 55-77 (ZX field). The ZXA2 switch 704-56 provides for the read out of the upper or lower 18 bits of RA and RQ registers 704-50 and 704-52 for address modification. The selected output signals from the ZXA2 switch and the ZXOB switch are applied to the ZX switch together with the RAAU, RTX and RIC register signals as shown.

The ZX switch selects as an output, bits of the RA/RQ/X registers for a 9-bit character string via a first position, X/RA/RQ bits for a 6-bit character string via a second position, RA/RQ/X bits for a 4-bit character string via a third position and X/RA/RQ bits for word type modification.

Positions five, six and seven are used for selecting the contents of the RAAU register, RIC register and RTX register respectively. A further ZXB2 switch 704-59 provides a second path to the unit 714 for read out of the program visible registers via the lines ZEBO-35. A similar path to the unit 728 is provided via the lines ZAQO-35.

The section 704-4 includes the registers and switches used for transferring commands and data to the cache 750. Such transfer operations normally require at least two cycles, one for sending an address and another for sending the data. Bits 5-8 of a command word are derived from the output of a four position switch 704-40. This switch receives a first constant value via a first position, the contents of a RZN register 704-42 via a second position, a second constant value via a third position and a third constant value via a fourth position.

Bits 1-4 of a command are applied by the circuits of block 704-1 to an OR gate circuit 704-44 together with bits 5-8. The OR gate 704-44 also receives via a ZADO switch 704-46 bits 1-8 of an RADO register 704-48. The RADO register 704-48 is an address and data out register which receives via a first position of a ZADOB switch 704-48 a logical (virtual) address from address preparation unit 704-3 via the lines ASFAO-35 and data output signals from the EU 714 via lines ZRESBO-35. The positions of the ZADOB switch 704-48 is under the control of the FMTD field for small CU format and the RADO field in the case of large CU format.

As seen from the Figure, either the ZZN1-8 bits or the ZADO bits 1-8 are applied as outputs to the RADO/ZADO lines as a function of the state of control signal [RADO-ZADO. Bits o and 1 are always binary ONES while bits 10-35 are furnished by the RADO register 704-46.

Additionally, the unit 704-5 of the preferred embodiment includes a four position selector ZREG switch 704-53 which is controlled by the coding of the CCSR field. The output of the ZREG switch is used to load the RREG register 714-42 with constant values or with signals corresponding to bit positions 24-26 of the RBIR register 704-152. On a next cycle, signals corresponding to the contents of RREG register 714-42 are transferred to the RRDXB register 704-189. In the case of instructions which reference CCS codes specifying instructions within the STR-SGL or STR-DBL classes, the same signals are transferred to the RRDXA register 704-158. Further, the contents of RREG register 714-42 may be loaded into RBASA register 704-156 under microprogram control.

EXECUTION UNIT 714--FIG. 3g

The unit 714 includes as major units, addressable temporary register banks 714-10 and 714-12, an arithmetic logic unit (ALU) 714-20, a shifter 714-24 and a scratchpad memory 714-30. Additionally, the unit 714 includes a number of multiposition data selector switches 714-15, 714-17, 714-22, 714-26, 714-28, 714-34, 714-36 and 714-38 to provide flexibility in selecting operands and output results.

In operation, the operands are selected via the ZOPA switch 714-15 and ZOPB switch 714-17 from one of the registers of the banks 714-12 and 714-10 or from other input lines such as ZEBO-35 or RDIO-35 as shown. The ALU 714-20 and shifter 714-24 performs operations upon the selected operands and the results are selected via the switches 714-24, 714-36 and 714-38 to be applied to the output bus lines ZRESA 0-35 and ZRESBO-35. Similarly, the contents of a scratchpad location selected via the contents of a scratchpad pad buffer 714-32 can be read out via the switches 714-34, 714-36 and 714-38.

The selected output results or other data are thereafter loaded into other registers within processor 700 including the temporary register banks 714-12 and 714-10 or the scratchpad memory 714-30 of execution unit 714.

In greater detail, the sources of operands are identical for both the ZOPA and ZOPB switches 714-15 and 714-17. The selection of switch position for the ZOPA switch and ZOPB switch is under the control of bits 9-12 and bits 13-16 of the microinstruction word. The ALU 714-20 performs logical, decimal or binary operations upon the selected operand data under the control of bits 24-28 of the microinstruction word of FIG. 6a.

The shifter 714-24 is a combinatorial logic network used to align, shift or rotate binary data under microprogram control. The input data signals from the ZSHFOP and ZEIS switches 714-28 and 714-22 can be viewed as being concatenated to form a single double word input. The shifter 714-24 provides a 36-bit output shifted in accordance with the shift count. The ZSHFOP switch 714-28 is controlled by bits 24-25 of the microinstruction word while the shift count is established by the sequence control constant fields (bits 138-143 of the microinstruction word of FIG. 6a which is appropriately selected via the auxiliary arithmetic control unit 722. For the purposes of the present invention, the ALU 714-20 and 714-24 may be considered conventional in design.

The scratchpad memory 714-30 provides a working space for storing various data required for the execution of certain instructions as well as various constants and descriptor values. For example, octal locations 10-15 are used to store an edit instruction table value required for carrying out edit operations. Writing into the scratchpad memory 714-30 involves first loading the RSPB buffer register 714-32 with input data applied via the ZRESB switch 714-38. During a next cycle, the contents of the register 714-32 are written into the location specified by the signals applied to the ZPSPA 0-6 lines by the AACU unit 722. Writing takes place when bit 22 of the microinstruction word (RSP field) is forced to a binary ONE.

As concerns the other switches, as mentioned, the results produced by the unit 714 are provided via the ZALU switch 714-26, the BSPDI switch 714-34, the ZRESA switch 714-36 and the ZRESB switch under microprogram control. The ZALU and ZSPDI switches provide a first level of selection to the ZRESA and ZRESB switches which provide a last level of selection. Since both the ZRESA and ZRESB switches have identical input sources, they can provide the same output data. The selection of ZALU switch data is under control of bits 30-31 (ZALU field) while the selection of ZSPDI data is under control of bit 23 (ZSPDI field). The selection of ZRESA and ZRESB data is under the control of bits 17-18 and bits 19-20 respectively of the microinstruction word of FIG. 6a.

The registers of banks 714-12 and 714-10 are addressed independently by bits 3-5 (TRL field) and bits 6-8 (TRH field) respectively. The first bit in each field specifies whether one of the four registers is to be addressed while the other 2 bits select the register to be addressed.

CHARACTER UNIT 720--FIG. 3h

It is seen that the unit 720 includes a bank of 4 registers 720-10, a number of registers 720-22, 720-24, 720-28, 720-30, 720-42, 720-46, 720-54, 720-63, 720-64, 720-68 and 720-70, the conversion logic circuits 720-27, adder networks 720-32 and 720-34, comparator network 720-72 and a number of decoder/detector networks 720-36, 720-38, 720-44, 720-48, 720-50, 720-56, 720-58 and 720-74 interconnected via a number of multiposition selector switches 720-26, 720-40, 720-62, 720-12 through 720-20. The control and selection of such switches and the strobing of the various registers is under the control of a number of flip-flop circuits included in block 720-80 and a pair of zero detector circuits 720-82 and 720-84.

The RCH bank of registers 720-10 are used as operand buffer registers for storing information received from the EU 714 via the ZRESA lines 0-35. A first register (OP1) is used to store the operand specified by descriptor 1 or data sent to unit 728 or unit 722. A second register (OP2) is used to store the operand specified by descriptor 2. Third and fourth registers (TABLE ENTRY 1, TABLE ENTRY 2) are used to store edit insertion table entry values obtained from EU 714.

The RCN1 register 720-28 holds the actual character position data for descriptor 1 which is used to select a character to be selected by ZCU switch 720-12. The RCN2 register 720-30 holds signals designating the character position data of descriptor 2. The contents are used to select a character from switch 720-14.

The ZCU and ZCV switches 720-16 and 720-18 are under the control of the ZCU and ZCV flip-flops of block 720-80. The RCN 1 and RCN 2 registers 720-28 are loaded under the control of the CN1 and CN2 flip-flops of block 720-80 in response to signals generated by decoder 720-56. This is done as a function of the character type (4, 6 or 9-bit characters) defined by the contents of the RTF1 and RTF2 registers 720-42 and 720-46 and the starting character position signals generated by the conversion logic circuits of block 720-27. The circuits of block 720-27 convert signals ZCNO-2 applied via switch 720-26 corresponding to an input character position value into an output character position. For 9-bit characters, there is no conversion necessary (i.e., input character position=output character position).

The two bit RTF1 register 720-42 holds the character type information relative to descriptor 1 while the two bit RTF2 register 720-46 holds the character type information for descriptor 2. The one bit RTF3 register 720-52 holds the character type information for descriptor 3. When descriptor 3 consists of 9-bit characters, the detector 720-50 sets the RTF3 register to a binary ONE. In all other cases, the RTF3 register is set to a binary ZERO. As seen from the Figure, these registers are loaded via switch 720-40.

The five bit RMOP register 720-70 stores the "micro-operation" values required for processing an edit instruction while the 4-bit RIF register 720-63 stores the information field (IF) values for such instructions. The 9-bit RCD register 720-64 is used during certain compare instruction operations for storing a first operand value. The 5-bit RTE8 register 720-68 stores the 5 most significant bits of the eighth edit insertion table entry value in response to a load signal generated by decoder 720-74 in response to a load command. The REFILL register 720-22 is used to store signals received from the unit 704-150 via the lines ZIDD 0-8. The RAD register 720-24 stores character position bits received from the unit 704-3 via the lines ASFA34-36.

The indicator flip-flops of block 720-80 store the result of an operation specified by the contents of the RMOP register 720-70. The indicators include a 2-bit MOP indicator A (MOPIA), a 3-bit MOP indicator B (MOPIB) and a 1-bit END indicator. The MOPIA indicators are decoded as follows:

00 go to MOP execute operation

01 go to LOAD MOP operation

10 Test MOPIB

11 n/a.

the MOPIB indicators provide additional status when the MOPIA indicators have the value "10". They are decoded as follows:

000--test the state of a length 1 indicator for underflow (L1UDF set when the output of the AXP adder equals 0 means L1 exhausted) and the state of the CN1 overflow indicator (CN1 OVF).

001--test the state of a length 3 indicator for underflow (L3UDF set when the output of the AL adder equals 0, means L3 exhausted) and the state of a CN3 overflow indicator (CNLOVF) which is set when the output of the AP adder equals 0.

010--test the states of the L1UDF, CN1OVF, L3UDF and CN30VF indicators.

011--decrement by 1, the length 2 value and test the states of the L3UDF and CN3OVF indicators during a first cycle and test the states of a length 2 underflow indicator (L2UDF) and the CN2OVF indicator during a second cycle.

100--test the states of the L3UDF, CN3OVF, L1UDF and CN1OVF indicators during a first cycle. Transfer the contents of the RAAU register to EU 714, decrement the length 3 value by 1 and increment and the CN3 value by one during a second cycle. During a third cycle, test the states of the L3UDF and CN3OVF indicators.

101--load the table entry value.

110--change the table values.

111--N/A.

The END indicator is set to indicate that the operation specified by the MOP value is complete.

THE AUXILIARY ARITHMETIC AND CONTROL UNIT (AACU) 722--FIG. 3i

The AACU 722 includes 3 parallel adder networks 722-2, 722-6 and 722-8 designated herein as a pointer adder network, an exponent adder network and a length adder network respectively. The pointer network 722-2 includes two banks of 4 registers (RP0-RP3 and RP4-RP7) 722-20 and 722-22. Each bank has its own multiposition switch (722-23 and 722-24) for selecting the data to be written therein and a pair of four position output switches for selecting the data to be read therefrom (i.e., switches 722-27, 722-28 and 722-29, 722-30). Additionally, bank 722-20 has a second input switch 722-32 whose output feeds the ZRPA switch 722-23 and provides for the selection of additional input data.

The ZRPC switch 722-32, the ZRPA switch 722-23 and the register bank 722-20 are jointly controlled by either bits 64-68 (ZRPAC field), bits 69-71 (ZRPAC-3 field) or bit 67 (ZRPAC-4 field) depending upon the microinstruction format. The ZRPA switch 722-23 can select one of the outputs from the ZRPC switch 722-32 via a first position, a value for loading a character offset for address modification/loading address register instructions for the character unit 720 via a second position and a character pointer value for a 9-bit character via a third position.

The ZPA switch 722-27 and the ZPB switch 722-28 select data from the RP0-RP3 register bank 722-20 under the control of bits 59-60 (ZPA) and bits 61-62 (ZPB) respectively. The ZRPB switch 722-24 and register bank 722-22 are jointly controlled by a single control field depending upon the type of microinstruction format bits 74-78 (ZRPB-0), bits 69-73 (ZRPB), bits 72-74 (ZRPB-3) or bit 68 (ZRBP-4). The ZRPB switch 722-4 can select the output of adder output switch 722-36 via a first position, an information field from the character unit 720 via a second position, a word or character pointer value for a 9-bit character via a third position and a character pointer value for a 9-bit character via a fourth and a fifth position.

The ZPC switch 722-29 and the ZPD switch 722-30 select data from the RP4-RP7 register bank 722-23 under the control of bits 57-58 (ZPC field) and bits 67-68 (ZPD field) respectively. As seen from FIG. 3, the outputs from the switches 722-27 through 722-30 are applied to the A and B operand switches 722-25 and 722-26. The outputs of these switches are applied to a pointer adder 722-34.

The ZAPA switch 722-25, the ZAPB switch 722-26 and the adder 722-34 are jointly controlled by a single control field bits 79-84 (AP field) or bits 82-83 (AP-3 field) depending upon the microinstruction format. As seen from the Figure, the ZAPA and ZAPB switches 722-25 and 722-26 select the outputs from the ZPA, ZPC, ZPB or ZPD switches or a constant value for application to adder 722-34.

A ZLX switch 722-36, a ZXC switch 722-38, a RSC register 722-40 and a ZRSC switch 722-42 operated under microprogram control are arranged to provide shift counts to the execution unit shifter. The ZSC switch 722-38 can also be used for loading data into the RP0-RP3 register bank 722-20 via the ZRPC and ZRPA switches 722-32 and 722-23 or into the RP4-RP7 register bank 722-23 via the ZRPB switch 722-24.

The selection of ZLX switch positions is controlled by bits 48-49 (ZLX field). The ZSC switch 722-38 is used to select one of the outputs of the ZLX switch 722-38 under the control of bits 50-52 (ZSC field). The RSC register 722-40 is loaded with the right most 6 bits from the output of the ZLX switch 722-38 under the control of bit 47 (RSC field). The two position ZRSC switch 722-42 selects which of two sources is to supply a shift count to the execution unit 714. Bit 84 (ZRSC field) selects either bits 138-143 (CNSTU/L field) or the RSC register 722-40 as a shift count source.

The last group of circuits shown in block 722-2 include a ZAAU switch 722-44 and a RAAU register 722-46 connected to receive the output of switch 722-44. The ZAAU switch 722-44 is used for transferring data to the register 722-46. From there the data is transferred via the section 704-5 to the execution unit 714 on the ZEB lines 0-35.

The inputs of the ZAAU switch 722-44 are selected by bits 50-52 (ZAAU field). The first position applies a 9-bit character output from the character unit 720 via the lines ZOC 0-8. The second and third positions are used for displaying the outputs from the length adder and exponent adders of blocks 722-6 and 722-8. The RAAU register 7-2-46 is loaded from the ZAAU switch 722-44 in response to bit 47 (RAAU field).

As seen from FIG. 3i, the exponent adder network 722-6 includes a single bank of 4 registers (RXPA-RXPD). The bank 722-60 has a multiposition switch 722-62 for selecting the data to be written therein and a pair of four position output switches for selecting data to be read therefrom (i.e., switches 722-64 and 722-66). The ZXP switch 722-62 and the RXPA-RXPD register bank 722-60 are controlled by bits 59-62 (ZXP field), bits 65-66 ZXP-1 field or bits 75-77 (ZXP-3 field).

A first position of the ZXP switch 722-62 is used to load the exponent result into register bank 722-60. The second position is used to store the result from the length adder 722-8. The next or third position is used for storing exponent values received from the character unit 720. Lastly, the fourth position is used for storing numeric scale factor information received from the RSIR lines 24-35.

The ZXPL switch 722-64 and ZXPR switch 722-66 select data from the register bank 722-60 under the control of bits 63-64 (ZXPL field) or bit 64 (ZXPL-1 field) and bits 65-66 (ZXPR field) respectively. The outputs from the switches 722-64 and 722-66 are applied as inputs to an A operand switch 722-68 and B operand switch 722-70 respectively. These switches apply selected inputs to a pair of 12-bit adders (AXP and AXM) of block 722-72 which generate an exponent output value applied to an output ZAXP switch 722-74. A single control field AXP (bits 69-73) controls the operation of the ZXPA switch 722-68, ZXPB switch 722-70, the adders, the ZAXP switch -22-74 and the loading of a RE register 722-76.

One adder AXM is arranged to receive the contents of the RE register 722-76 for providing absolute value when the sign of value generated by the AXP adder is negative (i.e., the AXP sign indicator not shown has control over the ZAXP switch selection).

The ZXPA switch 722-68 can select via a first position the contents of the RE register 722-76 or the output from the ZXPL switch 722-64 via a second position. The ZXPB switch 722-70 can select via a first position, a constant value, via a second position binary floating point exponent signals applied to the RDI lines 0-7, via a third position a numeric scale factor value applied to the RSIR lines 24-35, a fourth position the output from the ZXPR switch 722-66 and via a fifth position the output from the ZLNA switch 722-84.

The third adder network 722-8 for managing operand length data, similar to network 722-6, includes a single bank of 4 registers (RLN1-RLN4). The bank 722-80 has a multiposition switch 722-82 for selecting the data to be written therein and a pair of four position output switches for selecting data to be read therefrom (i.e., switches 722-84 and 722-86). The ZLN switch 722-82 and the RLN1-RLN4 register bank 722-80 are controlled by bits 59-63 (ZLN-1 field), bit 63 (ZLN-2 field) bits 79-81 (ZLN-3 field) or bits 79-83 (ZLN-4 field) depending upon microinstruction format.

The ZLN switch 722-82 applies the output of the length adder as an output via a first position, the output of the ZAXP switch 722-74 via a second position and a length field value from RSER lines 24-35 via a third position. Additionally, it applies a numeric length field value from RSIR lines 30-35 via a fourth position, a shift count value from RDI lines 11-17 via a fifth position and a length value from RCH lines 24-35 via a sixth position as inputs to register bank 722-80.

The ZLNA and ZLNB switches 722-84 and 722-86 select data from the register bank 722-80 under the control of bits 53-54 (ZLNA field) and bits 55-56 (ZLNB field) respectively as inputs to an A operand switch 722-88 and a B operand switch 722-90 respectively.

The outputs of these switches are applied as inputs to a 12-bit length (AL) adder 722-92. The ZALA switch 722-88, the ZALB switch 722-90 and AL adder 722-92 are all controlled by bits 74-78 (AL field). The ZALA switch 722-88 selects as an operand the output of the ZLNA switch via a first position, a constant field via a second position, the output of the ZPC switch via a third position and a numeric length field via a fourth position.

The ZALB switch 722-90 can select as an operand, a constant field via a first position, the output of the ZLNB switch 722-86 via a second position, the output of the ZXPL switch via a third position, a shift count value from RDI lines 11-17 via a fourth position, the output of the ZPC switch via a fifth position, the output of the ZPA switch via a sixth position and bit positions 6 and 7 of the ZPC switch 722-29 via a seventh position.

The unit 722 includes another group of circuits for furnishing a scratchpad address to unit 714. The circuits include a ZSPA switch 722-100, a RSPA register 722-102 and a ZRSPA switch 722-104, each controlled by bits 48-49 (ZSPA field), bit 47 (RSPA field) and bits 50-52 (ZRSPA field) respectively. The ZSPA switch 722-100 can select as an output, bits 91-97 corresponding to a scratchpad address field via a first position and the output of pointer adder 722-34 via a second position.

The ZRSPA switch 722-104 can select as an output, the contents of register 722-102 via a first position, a scratchpad address field via a second position and a descriptor value applied from the RSIR lines 32-35 via a third position and a value from the RSPR register of unit 704-150 via a fourth position. Additionally, the unit 722 includes a pair of registers 722-106 and 722-108 which are loaded with signals corresponding to bit positions 21-23 of RSIR register 704-154. One register is loaded when bit 53 of the microinstruction word of FIG. 6b or the FPOP flip-flop is a binary ONE. The registers are selected for loading in accordance with the states of the RDESC register 704-140 (00 or 10=R1DW; 011=R2DW).

The various control field signals used by the AACU 722 are derived from a decoder 722-110 which receives as inputs, the various microinstruction word bits loaded into a register 722-112.

CACHE UNIT 750--FIG. 4 General Description

The cache unit 750 is divided into five primary sections: a command buffer section 750-1, a control section 750-3, a cache directory section 750-5, a cache storage section 750-7 and an instruction buffer section 750-9.

COMMAND BUFFER SECTION 750-1

The command buffer section 750-1 includes a four word write command buffer 750-100 and a four word read command buffer 750-102 which are addressed via the counters 750-104 and 750-106. The write ZAC buffer 750-100 provides storage for a single ZAC write command while the read ZAC buffer 750-102 provides storage for up to four read ZAC commands.

The processor 700 transfers commands via the RADO/ZADO lines of interface 605 through the first position of a selector switch 750-110. The processor 700 transfers cache command information via the DMEM and DSZ lines through the first position of a selector switch 750-112. The states of these lines are held or stored in a register 750-114. As seen from the Figure, this information is also written into the buffers 750-100 and 750-102.

In addition to the cache command signals, the processor 700 sets a DREQCAC line. The processor 700 sets other control lines (e.g. HOLD-C-CU, CANCEL-C, CACFLUSH, BYPASS-CAC, READ IBUF, READ EVEN) when it wants to have the cache unit 750 perform other types of operations.

The states of the other control lines are decoded by a decoder 750-116 whose output is used to enable the ZAC buffers 750-100 and 750-102. Additionally, the processor 700 transfers zone bit signals for certain types of write commands via the lines DZDO-3. These signals are loaded into the RDZD register 750-132 via a switch 750-134. From there, the contents are applied via a switch 750-136 to a set of byte CBYSEL lines. Additionally, the signals on the DZO lines are applied to the MITS lines via a switch 750-139. Other zone signals (bits 5-8) are loaded into an RC address register 750-140 and thereafter applied to another set of byte CBYSEL select lines via a switch 750-142.

A plurality of busy bit registers 750-120 and 750-122 are used to determine which of the locations in the RZAC buffer 750-102 are available. The states of these registers are decoded via a priority decoder network 750-130 which selects the first available buffer location. The value developed is stored in the register 750-106 and is used as a write address for the read ZAC buffer 750-102. When the cache request involves doing a backing store (MEM memory) fetch (cache miss signaled by the state of signal BSPD), the appropriate busy bit or both busy bits are set in accordance with the number of SIU responses (ARDA signals) which will be generated. The busy bits are set by signals applied to a pair of lines SETBOTHBSY and SETONEBSY from a decoder, not shown, which decodes the particular command resulting in the application of a signal to one of the BSY lines. For example, a read signal command (not bypassed) causes two SIU ARDA responses, each response for bringing in a pair of words. Thus, both busy bits are set. In the case of a read single bypass command, there is only one SIU ARDA response. Hence, only one busy bit is set. Resetting of the busy bits takes place in response to the ARDA line via a RSPB register 750-124 which receives signals from the SIU 100 via the RMIFS lines.

In greater detail, the contents of registers 750-120 and 750-122 are set in accordance with the number of ARDA responses as mentioned when a PENBIT signal is a binary ONE (i.e., the pending bit corresponding to the block is not set). The decoder circuit 750-130 decodes the states of the busy bits and sets counter register 750-106 to the appropriate address value specifying the next empty location within read RZAC buffer 750-102.

The same address signals PRACW0-1 are also applied to a second position of the switch 750-139 in the case of read commands. From there, the signals are loaded into a 4-bit MITS register 750-138 and applied to the MITS lines. The main memory 800 operates to return the coded signals to cache unit 750 via the MIFS lines upon transferring the requested pairs of data words of a block. Thereafter, the signals are loaded into a 4-bit RMIFS register 750-125 and then into the RSPB register 750-124 when the control state signal THCFD is a binary ONE. The received value causes the resetting of the appropriate busy bit indications stored in registers 750-120 and 750-122.

It will be noted that the RMIFS but signals 2 and 3 are used to address read RZAC buffer 750-102 for read out of the appropriate command. Additionally, as explained herein, signals from an out pointer circuit (COUT), not shown, are used to access commands stored in read ZAC buffer 750-102. The busy bit indications stored in registers 750-124 and 750-126 are applied as inputs to the exclusive OR circuits of block 750-132. These circuits are operative to generate output signals indicative of the number of busy bits set. These outputs are in turn applied to different positions of a 4 position selector switch 750-133. By selecting the appropriate position or location, in response to the RMIFS bit signals 2 and 3, the switch 750-133 provides output signal SECRCV whose state determines when the cache unit 750 has received the second pair of words of a block. The SECRCV signal is applied as an input to block 750-3.

The outputs of the write ZAC buffer 750-100 and read ZAC buffer 750-102 are applied to different ones of a group of two position switches 750-150, 750-152, 750-154, 750-156 and 750-158. The output of ZAC buffer switch 750-150 is loaded into a SIU output register 750-174 via the switches 750-170 and 750-172. The output from the ZAC switch 750-152 is loaded into a pair of data register 750-180 via the switches 750-177 and 750-178.

The outputs of switches 750-154 and 750-158 are applied to a further switch 750-160 and stored in a holding register 750-162. The output of switch 750-156 is applied to a decoder 750-166 together with the DMEM outputs of switch 750-160. The other outputs from this switch are applied to a decoder 750-168. Additionally, the output of the switch 750-158 is applied to a decoder 750-164.

The decoder 750-166 decodes the cache commands received from processor 700 via the DMEMO-3 lines and those read out from the buffers 750-100 and 750-102 and generates signals for transferring commands to the cache storage 750-7 and directory 750-5. That is, the cache decoder 750-166 is used to control what information will be written into the cache storage 750-7 from the processor 700. The decoder 750-168 decodes the states of the BYPCAC and DSZ1 signals. It will be noted that the source of these last mentioned signals corresponds to processor 700 or switch 750-154.

The decoder 750-164 decodes the commands read out from the buffers 750-100 and 750-102 and generates signals for transferring commands to MEM memory (backing store) via the SIU 100. That is, the S decoder 750-164 is used to control the sending of information from the command buffers 750-100 and 750-102 to the SIU.

Additionally, the ZPSW switch 750-178 via a first position selects the ZAC command from the processor 700 on the RADO/ZADO lines for transfer to the SIU 100 on the DTS lines via the switch 750-172 or writes the main memory data into cache storage 750-7 via the RDO, RDI data registers 750-180. The second position of the ZPSW switch 750-178 applies the data output of the ZALT switch 750-177 to the DTS lines (ZAC data) or writes the main memory data from the DFS lines into cache storage 750-7 via the RDO, RDI registers 750-180 or transfers the ZAC commands to the processor 700 via the ZDI lines.

The ZACSW2 switch 750-170 is used to transfer a ZAC command (first position) or data from the ZAC buffer to the SIU 100 via the DTS lines (second position).

CONTROL SECTION 750-3

This section includes a number of control state flip-flops which generate signals for sequencing the cache unit 750 through the required cycles of operation for processing the various commands. Additionally, the section includes the necessary logic circuits for generating the required control signals during the required cycles of operation. For the purposes of the present invention, these circuits may be implemented in a conventional manner. Therefore, in order to simplify the description herein, only a brief description and the Boolean expressions will be given for certain control state flip-flops and control logic circuits as required for an understanding of the operation of the present invention.

The control state flip-flops generate a series of timing sequences which control the following data transfer sequences:

(1) processor to cache, SIU (operation to cache and to SIU);

(2) processor to SIU (transfer write data to SIU);

(3) zacbuf to cache (operation to cache);

(4) ZACBUF to SIU (operation to SIU);

(5) processor to ZACBUF (write data saved in buffer);

(6) SIU to cache, processor (2 words transferred);

(7) SIU to cache, processor (1 word transferred).

The transfers utilize the following flip-flops.

CONTROL STATE FLIP-FLOPS

The OATB flip-flop is the first flip-flop set in a first sequence which enables a transfer information from the SIU 100 to cache 750 and to the processor 750.

The OATB flip-flop is set for one cycle in accordance with the following Boolean expression: ARDA·DPFS.

The THCFD flip-flop is the next flip-flop set in the first sequence which enables the information received furing cycle OATB from the SIU 100 to be transferred to processor 700 via the ZDI lines. The THCFD flip-flop is set for one cycle in accordance with the following Boolean expression:

    SET: OETF=ARDA·DPFS.

the UG COGTH flip-flop when set permits the setting/resetting of a F/F bit, the setting of a pending bit, the setting of RR bits, writing MSA into the address of the directory section and writing data for write-single command into CACHE memory. It is set and reset in accordance with the following Boolean expressions:

    SET: HOLD·SET-COGTH.

    reset: (hold): cac:bsy1·no-hold-cac·cacbsy1+no-hold-cac.

the UGSOGTH flip-flop is the first set in a CPU to SIU sequence. When set, a first data word is put on the DTS lines. It is set for one cycle in accordance with the following Boolean expression:

    SET: HOLD·DWRT wherein DWRT=CWRT·SNG+CWRT·DBL+CWRT·RMT.

the CAOPR flip-flop is set in response to the read for an AOPR response. It is set for one cycle in accordance with the following Boolean expressions:

    SET: SSET-IN·CLD-IBUF(CBYP-CAC+BPSD)+CPR-RD·CBYP-CAC.multidot.BPSD+(CRD-SNG+CRD-DBL)·(CBYP-CAC+BPSD)+CRD-CLR+CRD-RMT+CWRT-SNG+CWRT-DBL+CWRT-RMT.

the CPR-FF flip-flop is used for determining when the cache unit will respond to a DREQ-CAC signal from processor 700. When this flip-flop is set to a binary ONE during a previous cycle, the cache unit will not respond to a request except in the cases of PREREAD, INST-F1, INST-F2, LDQUAD, RD-SINGLE or RD-DBL type commands. It is set and reset in accordance with the following Boolean expressions:

    SET: (CINST-F1+CINST-F2+CLD·QUAD+CRD·DBL+CRD·SNG).multidot.(CBYP·CAC+BPSD)+CPR-RD·CBYP-CAC·BPSD.

    reset: hold=rd-bsy.

the RBPSD flip-flop is used for turning off the processor 700 in the case of HOLD-ON-MISS or BYP-CAC condition. When the data comes back from the SIU 100, this flip-flop is reset except for an INST-F1 cycle. In the case of IF-1, after 4 words have been received from the SIU, this flip-flop is reset. It is set and reset in accordance with the following Boolean expressions:

    SET: SSET-IN·HOLD-CAN·CRP-RMT+CRD-CLR+(CINST-F1+CRD-SNG+CRD-DBL)·(CBYP-CAC+BPSD)

    reset: hold=thcfd·sec-rcv·cinst-f1+data-recov·inst-f1-ff.

control logic signals

1. the CPSTOP signal is the signal which is used to turn off the processor 700.

    CPSTOP=FBPSD=REQ CAC·[RDTYP·RZAC-ALL-BSY=PREF·(PR-RD+INST-F2+LDQUAD+RD-SNG+RD-DBL)+CAC-BSY1+CAOPR+UGCOGTH]+RBPSD+DBL·FF+PENBIT.multidot.FF+(RD-IBUF/ZDI·CAC-BSY-1)+(RD-IBUF/ZDI·LD-QUAD-FF)+(UGCOGTH·RD-DBL-CAC-BSY1).

2. the CAC-BSY1 signal indicates when the cache unit is busy. CAC-BSY1=OATB+THCFD.

3. The [$F/E-WRT signal is a write enable signal for setting and resetting the full/empty bits.

    [$F/E-WRT=CAC·BSY1·(UGCOGTH)·UGSOGTH·RD-DBL·BYP-CAC·DLY-BPSD·(INST-F2+LD-QUAD).multidot.BYP-CAC·DLY-BPSD.

4. the [$PEN1-WRT signal is a write enable signal for setting the operation pending bits.

    [$PEN1-WRT=CAC-BSY 1·(UGCOGTH)·(INST-F2+LD-QUAD+PR-RD+RD-SNG·DLY-BPSD+RD·DBL·DLY-BPSD).

5. the [$PEN2-WRT signal is a write enable signal for resetting the pending bits when all data associated with a request has been received from main memory.

    [$PEN2-WRT=THCFD·SEC-RCV·(INST-F2+LD-QUAD+PR-RD+RD-SNG+RD-DBL·BYP-CAC).

6. the RZAC-ALL-BSY signal indicates the busy status of the RZAC buffer established in accordance with the states of the busy bits.

    RZAC-ALL-BSY=(RBB-00+RBB-01)·(RBB-10+RBB-11)·(RBB-20+RBB-21)·(RBB-30+RBB-31).

7. the [$RMIFS signal is a write strobe signal which allows the multiport identifier bits to be stored when data or status information is received from main memory. These bits identify which location in the RZAC buffer contains the ZAC word associated with the received data (i.e., the data pertains to which of the several possible outstanding read requests).

    [$RMIFS=ARDA+AST.

8. the ALTSW0-DT signal enables incoming data from main memory to be saved in the RD0 and RD1 registers.

    ALTSW0-DT=CAC-BSY 1.

9. the ALTSW2-DT signal enables data from the ZAC buffer to be transferred to the RD0 and RD1 registers.

    ALTSW2-DT=DS-ALT+ALTSW0-DT.

    wherein DS-ALT=DS-11+DS-12+DS-13.

10. the signals OPSW0-DT through OPSW2-DT control the ZDI switch for transfers of data words from cache to processor 700 via the ZDI lines.

    OPSW0-DT=RD-IBUF/ZDI.

    opsw1-dt=rd-ibuf/zdi (req-cac+ugcogth)·wdsel0.

    opsw2-dt=rd-ibuf/zdi+wdsel1·(rd-sng+inst-f1)+req-cac·ugcogth·inst-f1+req-cac·ugcogth rdsng+req-cac ugcogth·dbl-ff.

11. the signals ZACSW1-LC1 and ZACSW2-LC2 control the switch 750-702 which selects the source address for all cache memory chips. The sources are the processor 700 when receiving commands, the ZAC buffer and the CADR address register.

    ZACSW1-LC1=ZACSW1-LC4·CAC-BSY-1·UGCOGTH.

    zacsw2-lc2=cac-bsy1+ugcogth.

12. the signal DATA-RECOV enables the processor 700 to recover from a stop condition (e.g. restrobe registers).

    DATA-RECOV=THCFD·(CINST-F1+CRD-SNG)·(FMIFS-1·WDSEL0+THCFD·CRD-DBL (FSMIFS-1·WDSEL0+FMIFS-1·WDSEL0+FMIFS-1·WDSEL0+CBYP-CAC)+THCFD·CRD-RMT.

13. the RD-BSY signal establishes when certain state flip-flops are reset.

    RD-BSY=RBB-00+RBB-01+RBB-10+RBB-11+RBB-20+RBB-21+RBB-30+RBB-31.

14. the SSET-IN signal is used to set certain state flip-flops.

    SSET-IN=RBPSD·CDBL-FF·PENBIT-FF·UGCOGTH.multidot.CAOPR·CAC-BSY1·[CPR-FF·CPR-RD·CINST-F2·CLD-QUAD·CRO-SNG·CRD-DBL]·[CRD-TYP.multidot.RZAC-ALL-BSY]·DREQ-CAC.

15.

    sec-rcv=rmifs-2·rmifs-3·[rbb-00αrbb-01]+rmifs-2.multidot.rmifs-3·[rbb-10αrbb-11]+rmifs-2·rmifs-3.multidot.[rbb-20αrbb-21]+rmifs-2·rmifs-3·[rbb-30αrbb-31].

16. the BPSD signal indicates a cache hit condition. ##EQU1##

wherein SP-i-00-14 corresponds to the address directory outputs (the saved address bits), F/Ei corresponds to the full/empty bit "i" and PENi corresponds to the pending bit "i".

It will be appreciated that in the above expressions that the symbols · denotes an AND operation, + denotes an OR operation, and α denotes an Exclusive OR operation.

CACHE DIRECTORY SECTION 750-5

This section includes a 4 level control directory 750-500 and a 4 level set associative address directory 750-502. The directory 750-502 includes 128 columns, each column being divided into 4 levels, 15 bits in length thereby providing space in each column for four blocks. The control directory 750-500 includes 128 10bit locations, each of which stores a 10-bit word of control information. The control information for each of the blocks includes two round robin (RR) bits, 4 full/empty (F/E) bits and 4 operation pending bits as shown.

The full/empty bits indicate whether a particular directory address has any significance (i.e., is valid). For a cache hit to occur, the F/E bit must be set to a binary ONE. A binary ZERO indicates the presence of an empty block. The round robin bits provide a count which indicates which block was replaced last. This count is incremented by 1 under the control of the full/empty bits by a counter 750-512 and is used to identify the next block to be replaced. As seen from FIG. 3, this operation takes place when the round robin and full/empty bits are read out into a pair of output registers 750-504 and 750-506. The full/empty bits are also read into a register 750-510 which controls the incrementing of the round robin bits. That is, the round robin bits are used after all the full/empty bits are set to establish which of the full blocks is to be used for new data. The resulting value (ADDRR0-1) is applied as an input to switch 750-518. All of the full/empty bits are reset by an initialize signal. The full/empty bits can be set via a register 750-516. When the processor 700 issues a read request which is a miss, during the state UGCOGTH, a value "1000" is loaded into the register 750-516. This value is written into the control directory 750-500. On the next request, the value "1100" is loaded into the register 750-516 and etc. until all the full/empty bits are set.

The operation pending bits are used to indicate when a particular operation is still outstanding. For example, the pending bits when set indicates that all the read data for a particular block has not been received. Accordingly, during a read operation, when the address directory signals a hit, with the pending bit set, the cache unit 750 halts the operation of processor 700. Hence, no new request is made to main memory.

The network for setting and resetting the operation pending bits includes a 4-bit buffer register 750-520, a block decode register 750-524 and a decoder 750-512. The registers 750-520, during a write cycle of operation, are addressed by the signals PRZACW0-1 via an address register 750-522 and signals MIFS2-3 during a read cycle. The block decode register 750-524 forces different ones of the output signals BKDCOD0-3 to binary ONES under the following conditions: (1) If at least one full/empty bit is a ZERO, when that bit is set to a binary ONE, the corresponding pending bit is set via the decoder 750-512. When all the full/empty bits are set, the next value for the round robin count is encoded and that bit position within the set of four pending bits is set to a binary ONE. A pending bit is reset via the decoder 750-512 only when the cache 750 has received all of the information (i.e., 4 words) from SIU 100. The contents of the registers 750-520 indicate the position of the pending bit to be reset. The pending bits read out from control directory 750-500 are applied as an input to decoder 750-514 for updating as required.

The pending bits are set and reset under the following conditions:

    SET: INSTF2(BYPCAC+CACMISS)+LDQUAD(BYPCAC+CACHEMISS)+PREREAD(BYPCAC·CACMISS)+READSINGLE·CACMISS+READDBL·BYPCAC·CACMISS

    reset: instf2+ldquad+preread+rdsng+rddbl·bypcac.

the actual control signals are as listed previously.

The address 750-502, as mentioned, contains 128 sets of 4 words, each 15 bits in length. Each 15-bit word corresponds to the address of a 4 word block in the cache storage section 750-7. Whenever, a ZAC command is processed and involves either writing to or reading from cache unit 750, the 15 bits of the block address contained in the ZAC buffers 750-1h0 or 750-102 are compared on a "set basis" with the address contents of the directory 750-502 to determine the presence of a hit or miss condition. More specifically, the directory 750-502 makes its associations on bits 0-14 of the ZAC address for detection of a hit or miss condition. These bits correspond to the address signals applied to either the ZAC 11-18, 20-26 lines or to the ZADO/RADO 10-24 lines selected via an input two position ZACSW switch 750-530.

The address of the directory set is defined by a cache address (CADDL0-6) applied via a three position input switch 750-702. This enables the referencing of 4 block addresses which are read out and applied as one input to each of a group of 4 comparator circuits 750-536 through 750-542. Each of the comparator circuits compares its block address with bits 0-14 of the ZAC address. The results generated by the circuits 750-536 through 750-542 are applied to corresponding inputs of a first group of AND gates 750-544 through 750-550 together with corresponding ones of the full/empty bit signals from register 750-506. A second group of AND gates 750-552 through 750-558 combine the outputs from AND gates 750-544 through 750-550 with signals ZEXTBK0-3 indicative of which block is being selected applied via register 750-518.

The AND gates 750-552 through 750-558 provide a group of output block selection signals (i.e., signals CBSEL0-3) which are applied as inputs to a cache storage 750-700 and to a group of directory hit detection circuits of block 750-560. The circuits of block 750-560 include a group of AND gates 750-562 which logically combine signals indicative of the operation pending bits with the block selection signals, the results of which are "ored" by an OR gate 750-564 to provide a directory hit signal on line BPSD. The circuits of block 750-560 force the line BPSD to a binary ONE when the address bits 0-14 match the directory contents, the corresponding full/empty bit is a binary ONE, and the corresponding pending bit is a binary zero. It is assumed there are error conditions.

Cache Storage Section 750-7

The section 750-7 includes a storage unit 750-700 having 2048 (2 K), 40-bit word locations organized into 128 sets of 4 blocks. The unit is constructed from bipolar chips, conventional in design. The cache storage unit 750-700 is addressed by the 7-bit address CADDL0-6 applied via the switch 750-702. The address is stored in a holding register 750-704. This causes 4 blocks of 4 words to be applied as inputs to a group of 1 of 4 selection switches (not shown). The appropriate block (level) is determined by the states of the block select signals applied to the CBSEL0-3 lines. The signals applied to the CBYSEL0-7 lines via switch 750-708 provide the appropriate selection of even word and odd word bytes. Between words 0, 2 and 1, 3 the byte selection is independent and proceeds as follows:

    ______________________________________                                                  OBYSEL0 (byte 0 is select)                                                     for words 0, 2                                                                 .                                                                              .                                                                              .                                                                              .                                                                              CBYSEL3 (byte 3 select)                                                        for words 0, 2                                                                 CBYSEL4 (byte 0 select)                                                        for words 1, 3                                                                 .                                                                              .                                                                              .                                                                              .                                                                              CBYSEL7 (byte 3 select)                                                        for words 1, 3.                                                       ______________________________________                                    

The signals applied via lines CWSEL0-3 via a decoder 750-706 is used for desginating the words. This ensures that the contents of the appropriate bit positions of the group of memory chips which comprise the unit 750-700.

The words of a selected block are applied as inputs to a number of sets of OR (NAND) gates 750-712 through 750-716. Each group of gates select the word of the selected block. The word outputs from the OR gates are applied as inputs to an instruction buffer 750-900 via a second position of a two position switch 750-902 and to the first 4 positions of an output ZDI switch 750-720 for forwarding to processor 700. The fifth position of the switch applies the word contents of registers 750-180 to processor 700 via a ZBP switch 750-902. Lastly, the sixth position of the ZDI switch 750-720 applies the output of the instruction buffer 750-900 via the ZIB lines 0-39.

As seen from the Figure, during a write cycle of operation, the word contents from the register 750-180 are applied as inputs to the unit 750-700.

Instruction Buffer Section 750-9

This section includes a 16 word instruction buffer 750-700 which receives data inputs from the registers 750-180 via the switch 750-902. As mentioned previously, the outputs from cache storage 750-700 are also written into the buffer 750-700 via the switch 750-902. Control signals and address signals applied via a switch 750-904 are decoded by a decoder 750-906 and are used to set a read address counter 750-908 and a write address counter 750-910 to the appropriate states. The address outputs of the counters are applied via a switch 750-912 and 750-914 to the buffer 750-900 and used to provide the appropriate addresses during read and write cycles of operation.

DESCRIPTION OF OPERATION

With reference to FIGS. 1 through 10e, the operation of the preferred embodiment of the present invention will now be described. Referrring first to FIG. 7, there is shown the sequences of control states utilized by the I cycle hardware circuits of block 704-102 during the execution of instructions within the classes listed in the Figure. As seen from FIG. 7, the control state FPOA is a beginning state for processing all instructions.

The FPOA state is entered when the FPOA control state flip-flop of block 704-102 of FIG. 3 switches to a binary ONE. This flip-flop is set to a binary ONE under hardware control in accordance with the following Boolean expression:

    SET=[HOLDI·(DIBFRDY·DIBFEMTY·[STRCPR·DXEDRPTS·DPIPE1-4).

that is, the FPOA cycle is entered following an [END cycle when there is no hold condition relating to the pipeline (i.e., signal HOLDI=1), the instruction buffer 750-900 is not empty (i.e., DIBFEMTY=1), it has at least one instruction ready for transfer to processor 700 (i.e., DIBFRDY=1), the previous instruction did not produce a sotre compare condition (i.e., [STRCPR=1), is not an execute or repeat instruction (i.e., DXED·RPTS=1) and pipeline operation has been started (i.e., DPIPE1-4=1). The STR-CPR flag is set to a binary ONE during a cache write operation when the address of the cache command equals the address of the instruction block.

When in control state FPOA, the RBIR register 704-152 stores the instruction op-code as well as the remainder of the instruction word having one of the formats illustrated in FIGS. 9a and 9b. Also, the RSIR register 704-154 stores the same instruction word. In the case of an instruction having the format of FIG. 9a, the RBASA register 704-156 stores the upper three bits of the Y field while the RRDX-A register 704-158 stores the td portion of the instruction word TAG field. The R29 flip-flop 704-162 stores the value of the AR bit 29 of the instruction word.

During control state FPOA, the hardware circuits of block 704-101 decode the CCS sequence field read out from the CCS control store 704-200 in response to the 10-bit opcode (bits 18-27) applied via the RBIR register 704-152. It is the coding of the CCS sequence field which establishes what path the processing of the instruction is to follow. Accordingly, the coding of the CCS sequence field determines the types of operations performed during the FPOA and subsequent cycles which complete as much processing of each instruction as possible under hardware control. Examples of the specific operations are set forth in the section "Hardwired Control State Actions" included herein.

Considering the paths in greater detail, it is seen from FIG. 7 that the hardware circuits of block 704-102 sequence from the FPOA state to control state FTRF-NG when a control flag flip-flop FTRF·TST indicates that the previous instruction was within the transfer class and that the condition for transfer or branching was not met ([TRGO=1).

As explained herein in the preferred embodiment of the invention, during control state FTRF-NG, the processor hardware circuits generate signals for reinitializing the instruction buffer as a function of the contents of the instruction counter. This enables the discontinuance of that stream of instructions and a change back to the current stream of instructions whose address is indicated by the instruction buffer circuits. The FTRF-NG control state is then followed by one of the cycles FPI-INIT through FWF-IBUF as a function of the coding of the I buffer status lines.

In the case of normal instruction processing, the path followed as a consequence of decoding the CCS sequence field is that labelled FTRF-TST+[TRG0. This path indicates that the previous instruction was not with the transfer class (FTRF-TST=1) or if it was within such class the condition for transfer is goint to be met ([TRG0=1). Hence, this path indicates continued processing of a transfer class instruction under hardware control. It will be noted that if the previous instruction was a transfer class instruction (FTRF-TST=1) and if the current instruction is a transfer class instruction (TRF), then the hardware circuits of block 704-102 remain in control state FPOA (i.e., follow path TRF to FTRF-TST).

The point X in FIG. 7 denotes from the coding of the CCS sequence field whether the particular instruction is in the EIS class, the ESC class or TRF·EA class, the EIS·ESC·[EA·TRF class or the EIS·ESC·EA class. In the case of the EIS class, the coding of CCS sequence field determines how many descriptors are needed for that particular EIS instruction. Each of the EIS instructions has the multiword format illustrated in FIG. 9b and can require up to three descriptors. The CCS fields for all instructions requiring one, two and three descriptors are grouped together within the decoding circuits. Additionally, signals applied via address lines of the instruction buffer circuits of the cache unit 750 are decoded to determine how many descriptor values or words are presently stored in the instruction buffer. These sets of signals are compared and when there are not enough descriptors presently in the I buffer to complete the instruction, then the circuits of block 704-102 switch from FPOA to control state FPIM-EIS. During control state FPIM-EIS, the processor circuits generate signals for conditioning the cache unit 750 to perform an instruction fetch operation for fetching four more words from main memory or backing store which are loaded into the instruction buffer.

Once the required numbers of descriptors have been fetched and the cache unit 750 signals that the instruction buffer is ready (IBUFRDY=1), the hardware circuits of block 704-102 are at point C. If the instruction buffer is not ready (IBUF-RDY=1), the hardware circuits 704-102 switch to control state FWF-DESC wherein the processor 700 waits for the descriptor. When the instruction buffer is ready (IBUFRDY=1), the hardware circuits are again at point C.

It will be noted that all EIS type instructions (CCS codes 110000-111111) follow a path to point C. If the CCS field indicates that the instruction is a bit type EIS instruction (BIT=1), then the hardware circuits 704-102 switch control state (FESC) without performing any FPOP cycles of operation. If the CCS sequence field indicates that the instruction is not within the bit type class (i.e., BIT=1), the hardware circuits 704-102 switch to control state FPOP for one cycle of operation. It will be appreciated that the number of descriptors within the EIS multiword instruction determines the number of FPOP cycles.

A maximum number of descriptors are processed under hardware control before the circuits 704-102 switch to control state FESC enabling control to be transferred to a microprogram routine within the execution control store 701-2. For those EIS multiword instructions which require address preparation on three descriptors, the hardware circuits 704-102 remain in the FPOP control state for executing two cycles during which the processor circuits generate addresses for the first and second descriptors before switching to control state FESC. As explained herein in greater detail, the aggrangement of the preferred embodiment permits further descriptor processing under hardwired control.

It is seen from FIG. 7 that depending upon the type of instruction as defined by control sequence field and the type of address preparation required, address preparation for the different descriptors proceeds until it is determined that address preparation can no longer continue under hardware control. More specifically, during the FPOP cycle, address preparation is performed for descriptors of the classes of instructions which include instruction types NUM2 through MVT conditioned on the fact that the descriptor is not an indirect descriptor (FID=1), that the descriptor does not specify an indirect length (FRL=1) and it is not a Type 6 descriptor (TYP6=1) or address preparation is to be completed under hardware control (FINH-ADR=1) in addition to other unusual situations which cannot be handled under hardware control (i.e., FAFI=1). When the circuits of block 704-104 force signal FINH-ADR to a binary ZERO, this indicates that the address preparation had been completed under microprogram control and therefore does not have to be performed during a FPOP cycle.

The circuits of block 704-110 force signal FAFI to a binary ONE when the address preparation can be accomplished during the FPOP cycle and there are no special conditions such as the occurrence of a mid instruction interrupt.

Lastly, the condition RDESC=00 is defined by the states of the flip-flops of block 704-142 and indicates the occurrence of a first FPOP cycle during which the processor circuits prepare the address of the first descriptor.

In the event that there are some special type of conditions presently defined by the function f, the hardware circuits of block 704-102 switch to control state FESC. This enables the transfer of control to routines stored in the ECS control store 701-2 for continuing the processing of the instruction under microprogram control.

Additionally, the circuits of block 704-102 include flip-flops which provide control states FIDESC and FWF-IDESC for processing under hardware control indirect operand descriptors for EIS instructions.

For a first indirect descriptor, it becomes necessary to hold up completion of the I cycle for a cycle and let the execution unit 714 complete its operation. As soon as the E cycle is completed, the processor circuits under hardware control fetch the indirect descriptor. In greater detail, when the CCS field indicates that the instruction is an EIS instruction and bit 31 of the RSIR register is a binary ONE (see FIG. 9c), this means that the first descriptor of the EIS instruction is an indirect operand.

During control state FPOA, the hardware circuits of block 704-102 hold up completion of the I cycle (i.e., HOLD-I=1) for one cycle. That is, a control flip-flop FPOAID included within block 704-102 is switched to a binary ONE in response to a first clock pulse which forces the [HOLDI00 signal to a binary ZERO. Upon the occurrence of a next clock pulse, the FPOAID flip-flop is reset to a binary ZERO which allows the [HOLDI00 signal to be forced to a binary ONE (see expressions listed under FPOA control state in "Hardwired Control State Actions" section).

For the remaining EIS descriptors, the hardware circuits of block 704-102 do not hold up the completion of any more I cycles following control state FPOA. From FIG. 7, it is seen that the control state FPOP is entered. However, the hardware circuits of block 704-102 immediately switch to control state FIDESC upon detection of an indirect descriptor. This state is followed by a switching to control state FWF-IDESC and a return to control state FPOP completing the processing of a first indirect operand descriptor. These states are repeated for each descriptor word specified by the MF field of the instruction word as having an indirect operand (see FIG. 9b).

Considering instructions other than EIS type instructions, it will be noted from FIG. 7 that when the CCS sequence field indicates that the instruction is within the escape class or within the transfer class and require indirect address modification, the hardware circuits 704-102 immediately switch from control state FPOA to the FESC control state. As mentioned, control is transferred to the appropriate microprogram routines stored in ECS control store 701-2. Thereafter processing of the instruction proceeds under microprogram control as explained here.

It can also be seen from FIG. 7 that non-EIS type instructions other than transfer class instructions (TRF=1) which require indirect addressing and are not within the escape class (ESC=1) follow a path which causes the hardware control circuits of block 704-102 to switch to control state FWF-IND. For execute double and repeat instructions, XED or RPT, the hardware control circuits 704-102 switch to control store FESC. Thereafter, indirect address preparation is performed under microprogram control.

In accordance with the preferred embodiment of the present invention, indirect address modification operations for instructions having the format shown in FIG. 9a are performed under hardware control. These include register then indirect (RI), indirect then register (IR) and indirect then tally (IT). Other IT address modification operations requiring other than indirection are performed under micoprogram control as explained herein.

As seen from FIG. 7, when register indirect address modification is required (i.e., the tm field specifies a register than indirect type modification), the hardware control circuits of block 704-102 switch from the FWF-IND control state to the FPOA control state provided that the CCS field indicates that the instruction is not an execute double or repeat instruction (i.e., RI·XED·RPTS+1).

The RI address modification is a 2T operation (i.e., FPOA (RI)→FWF-INT→FPOA). During control state FPOA, when the tm portion of the instruction word contents of the RSIR register 704-158 indicate RI address modification, the processor circuits inhibit the loading of the CCS field address into the ESC address register 701-10 of FIG. 3b. Also, the processor 700 takes action to fetch from memory the indirect word specified by the effective address resulting under R type modification (i.e., generates a read single memory command.

During control state FWF-INT, the processor 700 under hardware control transfers in for the indirect word, having the format shown in FIG. 9d, from cache unit 750 and forces the RI flip-flop of block 704-110 to a binary ONE. The RI flip-flop remains a binary ONE for the duration of the next FPOA control state. This flip-flop is used to force the R29 register 704-162 to a binary ZERO since the indirect word fetched from memory has its AR bit 29 set to a binary ONE (see FIG. 9d).

As seen from FIG. 7, when the tm field of the instruction specifies an indirect then register address modification and the instruction is other than an execute double or repeat (i.e., (IR+FIR)·XED·RPTS=1), the hardware control circuits of block 704-102 switch from the FWF-IND control state to the FIRT control state. The IR modification is a 3T operation (i.e., FPOA(IR)→FWF-IND→FIRT→FPOA). The same operations mentioned in connection with RI modification are carried out during control state FPOA.

During control state FWF-IND, the control state flip-flop FIRT and the FIR flip-flop are forced to binary ONES. This state is followed by control state FIRT during which the original contents of the RRDXA register 704-158 saved in the RRDXAS register 704-159 are transferred to RRDXA register 704-158 when the address modification specified by the indirect word is either of R or IT type. At this point, the development of an effective address is complete (last indirection).

Also, the control flip-flop FIRL is forced to a binary ONE. The FIRL (flip-flop indirect last) flip-flop remains a binary ONE for the duration of the next FPOA control state. Since the operation is not complete, the FIR flip-flop remains at a binary ONE during control state FPOA.

During the next control state FPOA, the FIRL flip-flop forces the R29 register 704-162 and RSIR tag bits 30-31 to binary ZEROS. This completes the I cycle of operation for that instruction. A similar sequence is followed in the case of a non-execute double or repeat instruction requiring an indirect then tally address indirect modification. This is a 3T operation (i.e., FPOA (IT)→FWF-IND→FIT-I→FPOA). During control state FWF-IND, in addition to loading the indirect word into the processor registers (i.e., ZDI→RSIR, RDI and RRDX-A, R29), the control state flip-flop FIT-I is forced to a binary ONE and the RRDXAS register 704-159 is forced to ZEROS.

During control state FIT-I, the ZERO contents of RRDXAS register 704-159 are loaded into RRDXA register 704-158. Also, the FIRL flip-flop is forced to a binary ONE. Similar to that described above, the R29 register 704-162 and RSIR tag bits 30-31 are forced to binary ZEROS by the FIRL flip-flop. The "Hardwired Control State Actions" section illustrates the various operations described above in greater detail.

As seen from FIG. 7, non-EIS type instructions which are not within the escape class and do not require generation of an effective address (EIS·ESC·EA) follow a path to point XX. These instructions have the format of FIG. 10a and their tm portion of their TAG fields are coded to specify no indirection (i.e., 00 code). As indicated, the tm portion of an instruction is tested for indirection during the FPOA cycle and when indirection is not specified, the control flag [EA is forced to a binary ONE state.

As seen from FIG. 7, the various groups of instructions following this path are those which reference CCS sequence fields coded to specify sequences listed within group A, group B, group C, TRF, STR-SGL, STR-HWU and STR-DBL. Instructions requiring group A sequences as well as those instructions whose processing has reached point B follow the path to point XXX. Point XXX in FIG. 7 indicates the point at which processor 700 has completed the I cycle processing of an instruction and must then fetch the next instruction from the I buffer for processing. Before that can be done, the processor 700 must make certain that the instruction just completed has not placed it in an execute double or repeat loop (i.e., the instruction is not an XED or RPT instruction). If the processor 700 has been placed in a loop, the hardware circuits of block 704-102 switch to control state FXRPT followed by control state FESC. This ensures that the processor 700 does not fetch the next instruction but instead control is transferred to the ECS control store 701-2 wherein the next operation(s) are carried out under microprogram control. More specifica-ly, during control state FXRPT, the processor 700 under hardwired control forces the ECS control store 701-2 to the appropriate address and during control state FESC transfers control from the hardware circuits.

When the CCS sequence field indicates that the instruction is not an execute double or repeat type of instruction and that the control flag STR-CPR is a binary ONE indicating that the instruction buffer must be reloaded because of a store operation, the hardware circuits of block 704-102 switch to control state FPI-INIT. As explained herein, in accordance with the teachings of the present invention, during state FPI-INIT, the processor 700 initializes the instruction buffer via the circuits of block 704-128. Thereafter, the hardware circuits of block 704-102 switch to control state FPIM-2 to fetch the next instruction. This state is followed by a return to control state FPOA as shown in FIG. 7.

When the CCS sequence field indicates that the instruction is neither an execute double or repeat instruction and the instruction buffer does not have to be reloaded because of a store compare operation ([STR-CPR=1), the hardware circuits of block 704-102 switch to one of three control states FPIM-1, FPOA and FWF-IBUF as shown. In the case where the instruction buffer is empty (IBUF-EMPTY=1), it switches to control state FPIM-1 to enable the fetching of instructions to fill the instruction buffer. After the instruction buffer has been filled, the hardware circuits of block 704-102 switch to control state FPOA to begin the processing of the next instruction. In the case where the buffer is not empty, (IBUF-EMPTY=1) but is ready for read out of the next instruction (IBUFRDY=1) the hardware circuits of block 704-102 immediately switch back to control state FPOA.

It will be noted from FIG. 7 that in the event the instruction buffer is not in a ready condition (IBUFRDY=1), the hardware circuits of block 704-102 switch to the FWF-IBUF control state and remain in that state until the instruction buffer is ready (IBUF-RDY=1). When it is ready, the hardware circuits of block 704-102 switch to control state FPOA.

It will be noted that instructions which reference CCS fields coded to specify the sequences listed in group B follow the path labelled group B wherein the hardware circuits of block 704-102 switch from control state FPOA to control state FESC. Similarly, instructions which reference CCS fields coded to specify the sequences listed in group C cause the hardware circuits of block 704-102 to switch to control state FDEL followed by control state FESC. In each case, these instructions require operations which cannot be executed by processor 700 under hardware control but which required certain microinstruction routines for completing the processing thereof as illustrated herein.

As seen from FIG. 7, the instructions which reference CCS fields coded to specify STR-SGL or STR-HWU sequences are processed under hardware control provided these instructions do not require character address modifications (FCHAR=1). In such cases, the hardware circuits of block 704-102 switch to control state FSTR.

Those instructions which reference CCS field codes specifying an STR-DBL sequence, the hardware circuits of block 704-102 switch from control state FPOA to the FSTR-DBL control state followed by control state FSTR. In the case of each of three types of sequences mentioned, the hardware circuits of block 704-102 follow a path back to point B for fetching the next instruction from the instruction buffer.

In accordance with the preferred embodiment, the path labelled TSXn is followed when the CCS field is coded to specify that the instruction is within the TSX class. Initially, the path is the same as that followed by instructions within the ESC-EA class. Hence, similar operations in generating an effective address are performed by processor 700 during control state FPOA. Additionally, the instruction counter is updated by being incremented by one.

The hardware circuits of block 704-102 then switch to control state FTSX1. During this state, the updated instruction counter contents are loaded into the RDI register 704-164. The hardware circuits of block 704-102 switch control flag flip-flop FTSX2 to a binary ONE and thereafter switch to cotrol state FPI-INIT. The control flag flip-flop FTSX2 causes the processor 700 to reference effective address generated during control state FPOA and stored in TEA0 during control state FPI-INIT. It will be appreciated that normally, the processor 700 references the address value IC+0+0 during control state FPI-INIT. The hardware circuits of block 704-102 then switch to control state FPIM-2 followed by control state FPOA.

The above actions as well as the other actions occurring during the control states of FIG. 7 are as indicated in the following section.

    __________________________________________________________________________     HARDWIRED CONTROL STATE ACTIONS SECTION                                        __________________________________________________________________________     FPOA CONTROL STATE                                                               If FINH-ADR= 1 then                                                            [Y(29) + X(RRDX-A) + ADR(29)] → ASEA;                                   [Y(29) + X(RRDX-A) + ADR(29)] + ZBASE → ASFA;                           If RSIR.sub.30-31 = 00 then 1 → EA*;                                    If RSIR.sub.30-31 ≠ 00 then 0 → EA; RBAS-A(29) →           RSPP;                                                                          If FINH-ADR = 1 then                                                           [0 + 0 + REA-T] → ASEA;                                                 [0 + 0 + REA-T] + ZBASE → ASFA;                                         1 → EA                                                                  ASEA → REA; ASFA → RADO                                          [$CACHE-REG = 1                                                                If FTRF-TST= 1 then 0 → FTNGO                                           If FMSK-29 = 1 then MASK R29 to 0                                              If FIRL = 1 then MASK RSIR 30, 31 to 00                                        0 → FIR                                                                 0 → FRI                                                                 0 → FIRL                                                                If  (FTRF-TST ·  [TRGO) · TRF · EA                  · EIS= 1 and                                                          if EA · (LD-SGL + LD-HWU + RD-CLR + EFF-ADR + NO-OP) then             1 → END; and                                                            if EA · (STR-SGL + STR-HWU + STR-DBL) = 1 then                        ZREG → RRDX-A; 0 → R29; and                                      if TSXn · EA = 1 then IC + 1 → IC                              CCS → CCS-REG; CCS-O.sub.0-1 → RTYP.sub.0-1 and                  if EA [DEL-STR-SGL + DEL-STR-DBL + TSXn + INST-GR] +                           [EA· ESC] = 1 where INST-GR = LD-SGL-ESC + LD-DBL-ESC                 + LD-HWU-ESC + EFF-ADR-ESC + ESC-EA then 00 → RBAS-B                    If FTRF-TST· TRF · EA = 1 then                               a. [INIT-IBUF = 1;                                                             b. CCS → CCS-REG;                                                       If FTRF-TST · [TRGO · EIS                                    If FREQ-DIR = 1 then [HOLD I = 1                                               If FREQ-DIR= 1 then RBIR.sub.27-35 → ZIDD.sub.27-35 →            R29,                                                                           RRDX-A, FID, FRL;                                                              If BIT = 1 then 01 → RTYP.sub.0-1 ;                                     If MTM-MTR = 1 then 00 → RTYP.sub.0-1 ;                                 If BIT· MTM-MTR= 1 then ZIB → RTYP.sub.0-1                     RIR.sub.30 → FAFI;                                                      ZIB → RSIR, RBAS-A;                                                     If  (NEED-DESC) · (IBUF-RDY) = 1 then                                 FTRF-TST= 1 then [READ-IBUF/ZIB (CUR) = 1                                      FTRF-TST = 1 then [READ-IBUF/ZIB (OPS) = 1                                     CCS → CCS-REG                                                           If FPOA-ID · RSIR.sub.31 then HOLD-I → 1                       If  FPOA-ID · RSIR.sub.31 · [HOLD-Ethen 1 →           FPOA-ID;                                                                       If FPOA-ID · [HOLD-E then 0 → FPOA-ID                        10.                                                                              If FTRF-TST = 1 and                                                            If [TRGO = 1 then Toggle FABUF-ACTV; If XED-RPTS = 1                           then 1 → FTRGP                                                          If [END= 1 then [RDI/ZRESB = 1                                                 If [TRGO = 1 then Inhibit IC Strobe;                                           1 → FTNGO                                                               0 → FTRF-TST                                                          DMEM AND VALUES GENERATED                                                      DURING CONTROL STATE FPOA                                                      [MEM, [SZ for FPOA                                                             If FTRF-TST · [TRGO = 1 then [MEM = None;                             If (FTRF-TST+ [TRGO) · ESC = 1 then [MEM = None;                      If (FTRF-TST+ [TRGO) · EIS = 1 then [MEM = None;                      If (FTRF-TST + [TRGO) · ESC· EIS· EA= 1 then        [MEM = Read                                                                    Single; [SZ = Sg1;                                                             (FTRF-TST+ [TRGO) · EA                                                If ESC-EA + DEL-STR-SGL + TSXn + DEL-STR-DBL + NO-OP = 1                       then [MEM = None;                                                              If LD-SGL + LD-SGL-ESC + LD-SGL-DEL then                                       FCHAR· RRDX-A = DU· DL= 1 then [MEM = Read Single;           [SZ = Sg1;                                                                     FCHAR· RRDX-A = DU = 1 then [MEM = Direct; [SZ = HWU;                 FCHAR· RRDX-A = DL = 1 then [MEM = Direct; [SZ = HWL;                 FCHAR = 1 then [MEM = None                                                     If LD-HWU + LD-HWU-ESC + LD-HWU-DEL =  1 then                                  RRDX-A =DU· DL= 1 then [MEM = Read Single; [SZ = HWU                  RRDX-A = DU = 1 then [MEM = Direct; [SZ = HWU                                  RRDX-A = DL = 1 then [MEM = Direct; [SZ = ZERO                                 If STR-SGL = 1 then                                                            if FCHAR= 1 then [MEM = Write Single; [SZ = Sg1 and                            if FCHAR = 1 then [MEM = None                                                  If TRF = 1 then                                                                if FTRF-TST· FABUF-ACTV = 1 then [MEM = Inst. Fetch-1;                [SZ = B and                                                                    if FTRF-TST· FABUF-ACTV= 1 then [MEM = Inst. Fetch-1;                 [SZ = A and                                                                    if FTRF-TST = 1 then [MEM = None                                               If EFF-ADR + EFF-ADR-ESC = 1 then [MEM = Direct; [SZ =  HWU                    If LD-DBL + LD-DBL-ESC + LD-DBL-FP-ESC = 1 then                                [MEM = Read Double                                                             If RD-CLR = 1 then [MEM = Read Clear                                           If STR-DBL = 1 then [MEM = Write Double; [SZ = DBL                             If STR-HWU = 1 then [MEM = Write Single; [SZ = HWU                             If LD/STR-SGL-ESC = 1 then [MEM = Read Single; [SZ = Sg1;                      [R/W = 1                                                                       If LD/STR-HWU-ESC = 1 then [MEM = Read Single; [SZ = HWU;                      [R/W = 1                                                                       FSTR CONTROL STATE                                                               REG(RRDX-A) → ZX;                                                       [ENAB-ZX-A2 = 1;                                                               ZX, ZX-A2 → ZDO;                                                        ZRESB → RADO;                                                           [END = 1.                                                                    FSTR-DBL CONTROL STATE                                                           REG(RRDX-A) → ZX;                                                       [ENAB-ZX-A2 = 1;                                                               ZX, ZX-A2 → ZDO;                                                        ZRESB → RADO;                                                           0010 → RRDX-A;                                                          1 → R29.                                                              FESC CONTROL STATE                                                             1. If [DIBUF/PIPE = 10 + 11 or [PIPE = 001 + 100] then                         [END = 1.                                                                      2. If [DIBUF/PIPE = 11 or [PIPE = 100 ] then 1 → FWF-REL.               FWF-IND CONTROL STATE                                                          ZDI → RDI                                                               If (RI + IR + IT-I) = 1 then ZDI → RSIR                                 ZDI → RRDX-A, R29                                                       If RI · (DXED-RPTS) = 1 then 1 → FRI                           If (IT-I) ·  ∥= 1 then 0 → RRDXAS.sub.0-3             If IR ·  ∥= 1 then RRDX-A → ZRDXAS.sub.0-3 and        1 → FIR.                                                                FIT-I CONTROL STATE                                                            1. RRDXAS → RRDX-A.sub.0-3                                              2. 1 → FIRL                                                             FIRT CONTROL STATE                                                             1. If RSIR-31= 1 then RRDXAS → RRDX-A and                               1 → FIRL                                                                FXRPT CONTROL STATE                                                            1. CCS → CCS-REG                                                        FTSX1 CONTROL STATE                                                            1. IC → ZX                                                              2. ZX → ZDO                                                             3. ZRESB → RDI                                                          4. 1 → FTSX2                                                            FDEL CONTROL STATE                                                             1. [0 + 0 + REA-T] → ASEA; and                                          [0 + 0 + REA-T] + ZBASE → ASFA.                                         2. ASEA → REA; ASFA → RADO; and                                  ZBASE.sub.33-35 → RBASE.sub.33-35 ; and                                 3. [$CACHE-REG = 1.                                                            4. If DEL-STR-SGL = 1 then [MEM = WRITE SGL; [SZ = SGL.                        5. If DEL-STR-DBL = 1 then [MEM = WRITE DBL; [SZ = DBL.                        6. If DEL-STR-SGL· DEL-STR-DBL= 1 then [MEM = NONE.                   7. If LD-SGL-DEL + LD-DBL + LD-HWU-DEL = 1 then [END.                          FPI-INIT CONTROL STATE                                                         1. If FTSX2= 1 then [0 + RIC + 0] → ASEA;                               If FTSX2 = 1 then [0 + 0 + REA-T] → ASEA;                               ASEA + ZBASE → ASFA.                                                    2. 0 → FTSX2                                                            3. ASEA → REA; ASFA →  RADO.                                     4. [$CACHE-REG = 1.                                                            5. ASEA → REA-T.                                                        6. Toggle FABUF-ACTV.                                                          7. [MEM = INST-FETCH1.                                                         8. [INIT-IBUF-OPS = 1.                                                         FTRF CONTROL STATE                                                             1. [4 + 0 + REA-T] → ASEA and                                           [4 + 0 + REA-T + ABASE → ASEA.                                          2. ASEA → REA; ASFA → RADO (force 00 → RADO.sub.32-33     ).                                                                             3. [$CACHE-REG = 1.                                                            4. RBAS-B → ZBAS-C; O, REA → RDI; 1 → FTRF-TST.           5. ZDI → RBIR, RSIR, RBAS-A, RRDX-A, R29.                               6. [READ-IBUF/ZIB (OPS) = 1.                                                   FTRF-NG CONTROL STATE                                                          1. [0 + 0 + REA-T] → ASEA; and                                          [0 + 0 + REA-T] + ZBASE → ASFA.                                         2. [END = 1.                                                                   FPIM-1 CONTROL STATE                                                           1. [4 + 0 + REA-T] → ASEA and                                           [4 (forces 00 → RADO.sub.32-33) + 0 + REA-T] + ZBASE →           ASFA.                                                                          2. ASEA → REA; ASFA →  RADO (force 00 → RADO.sub.32-3     3) and                                                                         [$CACHE-REG = 1.                                                               3. ASEA → REA-T; and                                                    [MEM = INST-FETCH1; and                                                        RBAS-B → ZBAS-C.                                                        FPIM-2 CONTROL STATE                                                           1. [4 + 0 + REA-T → ASEA.                                               2. ASEA → REA; and ASFA → RADO (force 00 → RADO.sub.3     2-33); and                                                                     [$CACHE-REG.                                                                   3. If ASFA-C27= 1 then ASEA → REA-T; ASFA, ZWS → RIB-VA,         RIB-WS; and                                                                    [MEM = INST-FETCH2; IPTR-CUR-SEL → [SZ;                                 and                                                                            If ASFA-C27 = 1 then [MEM = NONE; and                                          RBAS-B → ZBAS-C, and                                                    ZDI → RBIR, RSIR, RBAS-A, RRDX-A, R29, and                              [READ-IBUF/ZIB = 1.                                                            FWF-IBUF CONTROL STATE                                                         1. If IBUF-RDY = 1 then [READ-IBUF/ZIB (CUR) and                               ZIB → RBIR, RSIR, RBAS-A, RRDX-A, R29.                                  FPIM-EIS CONTROL STATE                                                         1. [4 + 0 + REA-T] → ASEA; and                                          [4 + 0 + REA-T] + ZBASE →  ASFA.                                        2. ASEA → REA, and ASFA → RADO (force 00 → RADO.sub.3     2-33);                                                                         [$CACHE-REG = 1.                                                               3. ASEA → REA-T; and                                                    [MEM = INST-FETCH1; and                                                        RBAS-B → ZBAS-C; ASFA-C27 → FEIS-STR-CPR; and                    ZIB → RSIR, RBAS-A; and                                                 If BIT· MTM-MTR= 1 then ZIB → RTYP.sub.0-1 ; and               If IBUF-RDY = 1 then [READ-IBUF/ZIB, and                                       CCS → CCS-REG.                                                          FWF-DESC CONTROL STATE                                                         1. If IBUF-RDY = 1 then [READ-IBUF/ZIB; and                                    CCS → CCS-REG.                                                          ZIB → RSIR, RBAS-A; and                                                 If BIT· MTM-MTR= 1 then ZIB → RTYP.sub.0-1.                    FPOP CONTROL STATE                                                             1. If FINH-ADR= 1 then                                                         [Y(29) EIS + X(RDDX-A, RTYP, FNUM) + ADR (29,                                  RTYP.sub.0)] → ASEA;                                                    [Y(29) EIS + X(RRDX-A, RTYP, FNUM) + ADR (29, RTYP.sub.0)]  +                  ZBASE → ASFA.                                                           2. If FINH-ADR = 1 then                                                        [0 + 0 + REA-T] → ASEA;                                                 [0 + 0 + REA-T] + ZBASE → ASFA.                                         3. If FID = 1 then                                                             HOLD-E = 1                                                                     RSIR → ZIDD                                                             ZIDD → RRDX-A, R29                                                      4. ASEA → REA; ASFA → RADO;                                      [$CACHE-REG = 1;                                                               If FIG-LEN = 1 then ZLN → RLEN                                          5. ASEA → REA-T (RDESC);                                                [FID + FRL + FAFI] → FINDA; (TYP=6) · FINH-ADR→         FINDC;                                                                         TYP=9 + FINH-ADR→ FINDB; FINDC + [SET-FINDC → DINDC;             FINDA + [SET-FINDA → DINDA;                                             FINDB + [SET-FINDB → DINDB.                                             6. RDESC = 00 (First Descriptor)                                               If FNUM· EDIT= 1 then                                                 RSIR.sub.21-23 → R1DW; RTYP.sub.0-1 → RTF1;                      If FIG-LEN = 1 then RSIR.sub.24-35 → RXPA, RLN1                         If FINH-ADR= 1 then ASFA.sub.34-35 → RP4                                ASFA.sub.34-35 → RP0 if RSIR21 = 1                                      ASFA.sub.34-36 → RP0 if RSIR21 = 1.                                     If FNUM· EDIT = 1 then                                                RSIR.sub.21-23 → R1DW; RTYP.sub.0-1 → RTF1; ASFA.sub.34-36       →                                                                       RCN1.sub.0-2                                                                   RSIR.sub.24-29 → RXPA;                                                  If FIG-LEN = 1 then RSIR.sub.30-35 → RLN1                               If RSIR.sub.21 = 1 then ASFA.sub.34-35 → RP0                            If RSIR.sub.21 = 1 then ASFA.sub.34-36 → RP0.                           If FNUM = 1 then                                                               RSIR.sub.24-29 → RXPA; RSIR.sub.21-23 → R1DW; RTYP0(O)           → RTF1;                                                                 ASFA.sub.34-36 → RCN1.sub.0-2                                           If FIG-LEN = 1 then RSIR.sub.30-35 → RLN1                               If RSIR.sub.21 = 1 then ASFA.sub.34-35 → RP0                            If RSIR.sub.21 = 1 then ASFA.sub.34-36 → RP0.                           A. If [FID· FRL· FAFI· (TYP=6+ FINH-ADR)] = 1       then                                                                           1. 0 → FINH-ADR, FIG-LEN                                                2. If MTM-MTRwherein DREV = MRL + TCTR + SCAN-REV = 1 then 1 =                 [READ-IBUF/ZIB; ZIB → RSIR, RBAS-A;                                     01 → RDESC; If TRANC= 1 then IR30 → FAFI;                        If TRANC= 1 then RBIR.sub.9-17 → ZIDD.sub.27-35 → R29,           RRDX,A, FID, FRL;                                                              If TRANC = 1 then ZIB → R29, RRDX-A;                                    If  SCAN· CMPC· CMPCT= 1 then ZIB → RTYP;             If EDIT = 1 then 0 → FNUM.                                              3. If [TCT + SCAN-FWD + MVT + CONV] · [ZLN.sub.24-35 = 0+             FIG-LEN] · FE11then                                                   MEM = PRE-READ.                                                                4. If (NUM2 + NUM3 + EDIT) (ZLN.sub.30-35 = 0+ FIG-LEN).                       FE11then                                                                       [MEM = PRE-READ.                                                               5. If MLR (ZLN.sub.24-35 = 0+ FIG-LEN) · FE11= 1 then                 (TYP=9) · FESCD= 1 then [MEM = LD QUAD;                               1 = [INIT-IBUF; and if                                                         (TYP=9 · FESCD=  1 then [MEM = PRE-READ.                              6. If (CMPC + CMPCT) (ZLN.sub.24-35 = 0+ FIG-LEN) · FE11              = 1 then                                                                       (TYPE=9) · FESCD= 1 then [MEM = RDSGL; [SZ = ZONED;                   (TYPE=9 ·  FESCD = 1 then [MEM = PREREAD.                             7. If OTHERWISE = 1 then [MEM = NONE.                                          B. If [FID· FRL· FAFI· (TYP=6+ FINH-ADR)] = 1       then                                                                           1. [MEM = NONE.                                                                7. RDESC = 01 (Second Descriptor)                                              If EDIT· FNUM= 1 then                                                 RSIR.sub.21-23 → R2DW, RTYP0-1 → RTF2;                           If FINH-ADR and RSIR21= 1 then ASFA.sub.34-35 → RP1                     RSIR21 = 1 then ASFA.sub.34-36 → RP1                                    ASFA.sub.33-35 → RP6.                                                   If FNUM· EDIT = 1 then                                                RSIR.sub.21-23 → R2DW, RTYP0-1 → RTF2;                           ASFA.sub.34-36 → RCN2.sub.0-2.                                          If FIG-LEN = 1 then RSIR.sub.30-35 → RLN2.                              If FNUM = 1 then                                                               RSIR.sub.24-29 → RXPB; RSIR.sub.21-23 → R2DW;                    RTYP0, (0) → RTF2; ASFA.sub.34-36 → RCN2.sub.0-2.                If FIG-LEN = 1 then RSIR.sub.30-35 → RLN2.                              A. If FID· FRL· FAFI· (TYP=6+ FINH-ADR) = 1         then                                                                           1. 0 → FINH-ADR, FIG-LEN.                                               2. If (NUM3 + EDIT) = 1 then                                                   RBIR.sub.0-8 → ZIDD.sub.27-35 → R29, RRDX-A,                     FID, FRL;                                                                      [READ-IBUF/ZIB (CUR); IR30  → FAFI                                      ZIB → RSIR, RBAS-A, RTYP.                                               3. If (NUM2 + NUM3 + EDIT) (ZLN.sub.30-35 = 0                                  + FIG-LEN) · FE21then                                                 [MEM = PRE-READ,                                                               10 → RDESC if NUM2 + NUM3.                                              4. (ZLN.sub.24-35 = 0+ FIG-LEN) · FE21.                               5. If (CMPC + CMPCT) = 1 then [MEM = PRE-RD.                                   6. If OTHERWISE = 1 then [MEM = NONE.                                          B. If FID· FRL·  FAFI (TYP=6+ FINH-ADR)= 1 then              1. [MEM = NONE.                                                                8. RDESC = 10 (Third Descriptor)                                               If  FNUM· EDIT= 1 then                                                RSIR.sub.21-23 → R1DW, If RTYP0-1 = 00 = 1 then 1 → RTF3         If RTYP0-1 ≠ 00 = 1 then 0 → RTF3                                 If FIG-LEN = 1 then RSIR.sub.24-35 → RLN1                               If FINH-ADR= 1 then ASFA.sub.34-35 → RP4;                               If RSIR.sub.21 = 1 then ASFA.sub.34-35 → RPO                            If RSIR.sub.21 = 1 then ASFA.sub.34-36 → RPO.                           If FNUM· EDIT = 1 then                                                RSIR.sub.21-23 → R1DW, If RTYP0-1 = 00 = 1 then 1 → RTF3         If RTYP0-1 = 00 ≠ 1 then 0 → RTF3                                 If FIG-LEN = 1 then RSIR.sub.30-35 → RLN1                               If RSIR.sub.21 = 1 then ASFA.sub.34-35 →  RPO                           If RSIR.sub.21 = 1 then ASFA.sub.34-36 → RPO.                           If FNUM = 1 then                                                               RSIR.sub.21-23 → R1DW; If RTYP0 = 0 = 1 then 1 → RTF3            If RTYP0 ≠ 0 = 1 then 0 → RTF3                                    If FIG-LEN = 1 then RSIR.sub.30-35 → RLN1                               If RSIR.sub.21 = 1 then ASFA.sub.34-35 → RPO                            If RSIR.sub.21 = 1 then ASFA.sub.34-36 → RPO.                           A. If [FID· FRLFAFI(TYP=6 + FINH-ADR)] = 1 then                       1. [MEM = NONE.                                                                B. If [SET-FESC = 1 then 1 → FESCD.                                     FIDESC CONTROL STATE                                                           1. [Y(29) + X(RRDX-A) + ADR(29)] → ASEA;                                [Y(29) + X(RRDX-A) + ADR(29)] + ZBASE → ASFA;                           ASEA → REA; ASFA → RADO;                                         [CACHE REG = 1;                                                                If DU + DL= 1 then [MEM = READ-SNGL; [SZ = SINGLE); 1 =                        [HOLD-E; 0 → FID; RBIR30 → FAFI;                                 If RDESC = 00 then RBIR.sub.27-35 → ZIDD → R29,                  RRDX-A, FRL;                                                                   If RDESC = 01 then RBIR.sub.9-17 → ZIDD → R29, RRDXA,            FRL;                                                                           If RDESC = 10 then RBIR.sub. 0-8 → ZIDD → R29, RRDX-A,           FRL.                                                                           FWF-IDESC CONTROL STATE                                                        1. ZDI → RBIR, RBAS-A;                                                  HOLD-E = 1                                                                     If RDESC = 00 and                                                              if BIT· MTM-MTR= 1 then ZDI = RTYP                                    If RDESC = 01 and                                                              if (SCAN + CMPC + CMPCT) = 1 then ZDI → RTYP                            If RDESC = 10 then ZDI → RTYP.                                          __________________________________________________________________________      *The bracket sign ([) has been omitted from the term EA throughout for th      sake of clarity.                                                         

    __________________________________________________________________________     ABBREVIATIONS OF TERMS USED IN THE                                             HARDWIRED CONTROL STATE ACTIONS SECTION                                        __________________________________________________________________________       Y(29)         = R29 = RSIR.sub.0-17 →ZY                                               R29 = RSIR.sub.3,3,3,3-17 →ZY                             Y(29) EIS     = R29 = RSIR.sub.0-20 →ZY                                               R29 = RSIR.sub.3,3,3,3-20 →ZY                             X(RRDX-A)     =  RSIR.sub.30 = ENAB-ZX as a function of                                      RRDX-A                                                                         RSIR.sub.30 = DISABLE ZX                                       4 ADR(29)       = R29 = 0→ZZ.sub.0-20                                                   R29 = ZAR.sub.0-19 →ZZ.sub.0-19 ;                                       0→ZZ.sub.20                                               RBAS-A(29)                                                                     RSPP          = R29 = 0010→RSPP.sub.0-3                                               R29 = 1,RBAS-A.sub.0-2 →RSPP.sub.0-3                      [READ-IBUF/                                                                    ZIB(CUR)      = [READ-IBUF/ZIB                                                               FABUF-ACTV = 0→DRDB                                                     FABUF-ACTV = 1→DRDB                                       [READ-IBUF/                                                                    ZIB(OPS)      = [READ-IBUF/ZIB                                                               FABUF-ACTV = 1→DRDB                                                     FABUF-ACTV = 0→DRDB                                       [END          = If  XEDRPTRPLRPDXEC then                                                     ZIB→RBIR, RSIR, RBAS-A, RRDX-A, R29;                                    If FTRF-TST.[TRGO = 1 and                                                      If ( IBUF-EMPTY . IBUF-RDY) = 1 then                                           [READ-IBUF/ZIB(OPS);                                                           If FTRF-TST = 1 and                                                            If EIS + FTRFNG = 1 then IC + 1→IC;                                     If EIS . FTRFNG = 1 then IC + CCS-R.sub.1-3 →                           IC;                                                                            If ( IBUF-EMPTY . IBUF-RDY) = 1 then                                           [READ-IBUF/ZIB(CUR);                                                           If FTRF-TST = 1 then 0→FINH-ADR.                          RI            = RSTR 30 . 31.                                                10.                                                                              IR            = RSIR 30 . 31.                                                  IT-I          = (RSIR 30 . 31) (RRDX-AO . 1 . 2 . 3).                          X(RRDX-A, RTYP, FNUM                                                                         = ENABLE ZX as a function of RRDX-A,                                           RTYP, FNUM.                                                      ADR(29, RTYP.sub.0)                                                                          = R29 = 0→ZZ.sub.0-20                                                   R29 = ZAR.sub.0-19 →ZZ.sub.0-19 ;                                       RTYP.sub.0 = ZAR20 + 21.22 +                                                   21.23→ZZ20                                                               RTYP.sub.0 = 0→ZZ20.                                     ASEA→REA-T (RDESC)                                                                    = ASEA→REA-T                                                            RDESC = 00 = 000→ZBAS-C                                                 RDESC = 01 = 001→ZBAS-C                                                 RDESC = 10 = (01, FABUF-ACTV)→                                          ZBAS-C.                                                          [$RTYP-B      = If BIT = 11→RTYP-B.sub.0-1                                            If BIT = RTYP.sub.0, RTYP.sub.1 . FNUM→                                 RTYP-B.sub.0-1. -16. [$CACHE-REG = STROBE CACHE CONTROL                        REGISTERS.                                                       CCS→CCS-REG                                                                           = ZREG(CCS-R→RREG→RRDX-B on                                      next clock pulse; CCS-02→FNUM.                            TYP9          = RTYP.sub.0 -  .sub.1 -  + RTYPO FNUM.                          TYP6          = RTYP.sub.0 -  .sub.1 . FNUM.                                 __________________________________________________________________________

While it is desirable to have processor 700 execute instructions in a pipeline fashion, there are different types of instructions which cannot be executed in the pipeline mode. These include instructions within the ESC class, instructions which process data in byte or digit form and instructions within other classes such as ESC-EA, LD-SGL-ESC, etc.

When the processor 700 establishes by means of the CCS code referenced by an instruction that the instruction cannot be completely executed in a pipeline mode of operation, the I cycle circuits of block 704-102 switch to the control state ESC. From FIG. 7, it is seen that the point of I cycle processing which this occurs varies as a function of instruction type or CCS sequence. At this point, the processor 700 transfers control to the microprogram sequence for completing the execution of the instruction.

Following completion of the sequence, the processor 700 restarts its pipeline mode of operation. In accordance with a preferred embodiment of the present invention, restarting pipeline operation from control state ESC is provided by different code combinations of the PIPE microinstruction field.

The types of restarts are coded as follows.

    ______________________________________                                         [PIPE DESIG-                                                                   CODE  NATION    OPERATION                                                      ______________________________________                                         0001  TYPE 1    This is a restart and release                                                  operation wherein the processor                                                700 is returned to control state                                               FPOA to begin processing of the                                                next program instruction. That                                                 is, this code causes the RBIR                                                  register to be loaded with a new                                               instruction, the advance of the                                                I buffer address pointer and the                                               performance of an [END cycle of                                                operation. These operations                                                    are as follows:                                                                ZIBO-35→RBIRO-35;                                                       ZIBO-35→RSIRO-35;                                                       ZIB29→R29;                                                              ZIB32-35→RRDXA; and                                                     ZIBO-2→RBASA.                                           0010  TYPE 2    This is a restart and release                                                  operation wherein the processor                                                700 is returned to control state                                               FPOA to continue processing of                                                 the current instruction. That                                                  is, this code causes restarting                                                without loading the RBIR, RSIR,                                                etc. registers with a new                                                      instruction.                                                   0011  TYPE 3    This is a restart operation where-                                             in the processor 700 is returned                                               to control state PI-INIT. At                                                   this point, the processor 700                                                  fetches two four blocks of in-                                                 structions which are loaded into                                               the I buffer and the transfer of                                               a first instruction into the                                                   RBIR, RSIR, etc. registers.                                                    The instruction in and out address                                             pointers are initialized to point                                              to the start of the new blocks                                                 of instructions. Prior to the                                                  restart, the RIC, IBASE, etc.                                                  are loaded under microprogram                                                  control and instruction processing                                             under hardware control begins                                                  at control state FPOA.                                         0100  TYPE 4    This is a restart and wait                                                     operation wherein pipeline opera-                                              tion is started under micropro-                                                gram control before the processing                                             of the current instruction is                                                  completed. That is, this code                                                  causes the processor 700 to                                                    perform an [END cycle for loading                                              the RBIR, RSIR, etc. registers                                                 with the next instruction and                                                  return to control state FPOA.                                                  The processor 700 remains or waits                                             until a type 5 release is                                                      generated under microprogram                                                   control before completing the                                                  following cache cycle.                                         0101  TYPE 5    This is a release operation                                                    wherein the waiting processor                                                  700, restarted by a type 4 code,                                               begins pipeline operation                                                      following the type 5 release.                                  0110  TYPE 6    This is a restart operation                                                    used during the processing of                                                  EIS instructions wherein the                                                   processor 700 is returned to                                                   control state FPOP.                                            0111  TYPE 7    No operation is performed in                                                   response to this code.                                         ______________________________________                                    

The above restart operations will now be considered in greater detail with reference to FIG. 8 and FIGS. 10a through 10e. The first or type 1 restart is illustrated in FIG. 10a. It is assumed that the instruction being processed specifies a store byte of Q register (STBQ) operation. This instruction has the format shown in FIG. 9a. Bytes of the Q register are transferred into the corresponding byte positions of the location specified by the Y address field. The binary ONES in the tag field of the instruction specify the byte positions of Q and Y that are affected by the instruction.

During control state FPOA, the op-code value (552) of the instruction references a location within CCS store 704-2 containing a CCS word coded as indicated in FIG. 8. The CCS address applied via the bus 704-204 is loaded into the ECS address register 701-10 of FIG. 3b. Also, the CCSR field of the CCS word conditions the switch 704-53 to load the code specifying the Q register for selection into RREG register 704-55.

At the beginning of the next or second cycle, since the CCSS field is coded to specify that the STBQ is within the ESC class, the hardware circuits of block 704-102 switch from control state FPOA to control state FESC as shown in FIGS. 8 and 10a. During this state, no cache command is generated. However, the contents of the RREG register 704-55 are loaded into the RRDXB register 704-189.

During the third cycle, the processor 700 executes operation specified by the instruction under the control of the microinstruction routine whose starting address is specified by the CCSA field of the CCS control word. That is, during the third cycle, which corresponds to a first E cycle, the address preparation unit 704-3 under microprogram control sums the values Y (29)+X (RRDXA)+AR (29) producing a result effective address which is loaded into RADO register 704-46 via the ASFA lines. Also, under microprogram control (i.e., DMEM field), the processor 700 generates a write single (zoned) command via the switch 704-40. This command which includes the address in the RADO register 704-46 is transferred to cache unit 750 via the RAD0/ZADO lines.

During the next cycle (second E cycle), the contents of the Q register selected by the contents of the RRDXB register 704-189 are loaded into the RADO register 704-46. It is also seen from FIG. 10a that the cache unit 750, in response to the cache command, executes a cache write single cycle of operation wherein the cache unit 750 transfers the command to main memory 800 via the DTS lines. Also, when the word location specified by the cache command address resides in cache store 750-700, the selected bytes of the Q register contents are written into cache store 750-700. During the next cycle, the cache unit 750 transfers the Q register contents to main memory 800 via the DTS lines.

As seen from FIGS. 8 and 10a, the microinstruction word controlling the operations of processor 700 includes a DPIPE field coded to specify a type 1 restart. As seen from FIG. 7, the processor hardware circuits of block 704-102 switch to one of four control states FXRPT, FPI-INIT, FPIM-1 or FPOA (i.e., point B) depending upon the conditions shown.

In greater detail, the circuits of block 704-102 switch to control state FXRPT when the instruction is either an XED or RPT type instruction. When the instruction is not an XED or RPT and there was a store compare condition, the circuits of block 704-102 switch to control state FPI-INIT. However, the circuits of block 704-102 switch to control state FPIM-1 when the instruction is neither an XED nor RPT, there is no store compare condition and the I buffer is empty. If the previous conditions are the same but the I buffer is not empty but in a ready state, the circuits of block 704-102 switch to control state FPOA.

From the above, it is seen that by including a [PIPE field coded to specify a type 1 restart, the processor 700 is able to start its pipeline processing by beginning the processing of the next instruction, notwithstanding the type of instruction whose execution was required to be completed under microprogram control.

It will be noted that in the case of the STBQ instruction, it was not necessary to examine the TAG field of instruction before transferring control to routines within the ECS control store 701-2. However, there are a number of instructions wherein the processor 700 examines the tag fields. These instructions include basic operations instructions such as those specifying load and store operations.

FIG. 10b illustrates the manner in which a load A (LDA) instruction is processed. This instruction which has a format of FIG. 9a is assumed to include a tag field coded to specify an indirect then tally (IT) address modification requiring other than indirect addressing (indirection). As seen from FIG. 10b, the processor address preparation unit 704-3 generates an effective address which serves as the command address. This address is loaded into RADO register 704-46. Since the CCS field specifies a LD-SGL sequence, the circuits of block 704-108 generate a read single command to be issued to cache unit 750 under hardware control. The command bits 1-4 and zone bits 5-8, as mentioned, are generated by the circuits 704-118 and switch 704-40. The zone bits 5-8 are set to binary ONES since they are not used for read commands.

The processor circuits within block 704-110 decode the contents of bit positions 30-31 of RSIR register 704-154 while the circuits of block 704-102 decode the CCS sequence field. Since the tag field indicates an IT address modification requiring other than indirection (i.e., incrementing or decrementing of values) and the CCS field indicates that the instruction is not within the EA, ESC or EIS class, the circuits of block 704-102 switch to control state FWF-IND. When in this state, processor 700 forces the ECS control store 701-2 to location 12.

As seen from FIG. 10b, during the second cycle, the cache unit 750, in response to the read single command, executes a cache cycle of operation. Assuming that the word requested resides in cache store 750-700, the cache unit 750 reads out the word and applies it to the ZDI lines. During the concurrent I cycle, the processor 700 loads the word into the RSIR register 704-154. Next, the circuits of block 704-102 switch to the control state FESC. At this time, control is transferred to the indirect tally routine which begins at location 12.

During a number of the E cycles, the tally routine generates an effective address as a function of the IT address modification specified. The resulting address is loaded into the TEAO register of bank 704-302. Prior to completing the execution of the indirect tally routine, the processor 700 reads out as the last microinstruction word of the routine one containing a [pipe field coded to specify a type 2 restart. As seen from FIG. 10b, the processor circuits of block 704-114, upon decoding the [PIPE code, generate signals which switch the circuits of block 704-102 to control state FPOA.

At this point (fifth cycle), the processor 700 begins its processing of the LDA instruction utilizing the effective address generated by the indirect tally routine. As seen from FIG. 10b, during control state FPOA, the effective address contents of TEAO are loaded into RADO register 704-46. Also, during control state FPOA, the address of the CCS word is loaded into the ECS address register 701-110 of FIG. 3b. In the manner previously described, the processor 700, under hardware control, generates a cache read single command utilizing the generated effective address. Also, the CCSR field of the CCS word conditions the switch 704-53 to load the code specifying the A register for selection into RREG register 704-55.

During the next cycle (sixth cycle), the cache unit 750, in response to the read single command, executes a cache cycle of operation. Assuming that the requested word resides in cache store 750-700, the cache unit 750 reads out the word and applies it to the ZDI lines. Also, under hardware control, the contents of RREG register 704-55 are loaded into the RRDXB register 704-189.

During the E cycle (seventh cycle), the processor 700, under control of the microinstruction word specified by the CCS address, completes the execution of the instruction by transferring the word from cache unit 750 into the A register selected by the contents of the RRDXB register 704-189.

From the above, it is seen that by including a microinstruction word containing a [PIPE field coded to specify a type 2 restart within a routine, the processor 700 is able to continue the processing of the same instruction following the execution of certain address generation operations which are more expeditiously carried out under microprogram control.

Certain types of instructions require transfers of control when switching between different modes of operation required to be carried out under microprogram control. One such instruction is a transfer and set slave (TSS) which has the format shown in FIG. 9a. As illustrated in FIG. 10c, the type 3 restart facilitates the processing of this type of operation by the processor 700 when operated in a pipeline fashion.

As seen from FIG. 8, the op-code (715) of this instruction causes the read out of a CCS word from control store 704-2 which is coded as indicated. During the first cycle, while the processor 700 is in control state FPOA, the address preparation unit 704-3 generates an effective address which is stored in temporary register TEAO. Since the CCS field specifies an ESC-EA sequence, the circuits of block 704-102 switch to control state FESC. At the end of the second cycle, the processor 700 transfers control to the routine at location 2066 of the ECS control store 701-2 specified by the CCS address previously loaded into the ECS address register 701-10 during control state FPOA.

As seen from FIG. 10c, the processor 700, under microprogram control, loads the instruction counter with the address of a new block of instructions and resets a master slave mode indicator to the slave mode. During the last cycle (fourth cycle) of the routine, a microinstruction word is read out from the ECS control store 701-2 which includes a [PIPE field coded to specify a type 3 restart. The decoder circuits of block 704-114 in turn generate signals which the I cycle control circuits of block 704-102 to control state FPI-INIT.

As seen from FIG. 10c (fifth cycle), processor 700, under hardware control, transfers the IC address to RADO register and the temporary storage register TEA and generates a cache IFETCH1 command including the address to cache unit 750. Also, the processor 700 forces the INITIBUF line to a binary ONE which clears the other portion of the I buffer. The circuits of block 704-102 are conditioned to switch to control state FPIM-2.

During the next cycle (sixth cycle), the address preparation unit 704-3 increments the IC address by 4 and loads it into the RADO register 704-46 and into temporary storage register TEA. Also, the processor 700 generates a cache IFETCH2 command to cache unit 750.

Assuming the instruction blocks reside in cache store 750-700, during cycles 6 and 7, the cache unit 750, in response to the IFETCH1 and IFETCH2 commands, fetches first and second blocks of instructions respectively from cache store 750-700 and loads them into the I buffer. It will be noted that at the end of cycle 6, the I cycle circuits of block 704-102 switch to control state FPOA to start the processing of the next instruction concurrent with generating the IFETCH2 cache command.

From the above example, it is seen how the processor 700 is able to execute under microprogram control operations required for switching control to another mode and thereafter be forced to a predetermined control state so as to resume its pipeline mode of operation at a point wherein the required blocks of instructions are fetched automatically to begin execution of a new block of instructions.

FIG. 10d illustrates the types 4 and 5 restarts. It is assumed that processor 700 is beginning the processing of a floating point add (FAD) instruction followed by a series of load A (LDA) instructions all of which also have the format shown in FIG. 9a. In processing such instructions, the processor 700 is required to perform a number of E cycles of operation to complete the execution of the instruction. However, it is advantageous to start processing of other instructions in a pipeline fashion concurrent with such execution. The arrangement of the present invention permits such processing.

As seen from FIG. 8, during control state FPOA (first cycle), the processor address preparation unit 704-3 generates an effective address. The op-code of the FAD instruction causes the processor 700 to reference a location within control store 704-2 having the format and values shown. Since the CCSS field is coded to place this instruction within the LD-SGL-ESC class, the I cycle circuits of block 704-102 switch to control state FESC at the end of the first cycle.

Additionally, the processor circuits in accordance with the CCS code generates a read-single cache command including the effective address loaded into RADO register 704-46. In response to the cache command, the cache unit 750 executes a cache cycle of operation (second cycle) to fetch the requested data word. Assuming that the data word resides in cache store 750-700, the cache unit 750 transfers the data word to the RDI lines during this cycle.

At the start of a third cycle, the processor 700 will have to begin execution of the floating point add operation under control of the microprogram routine having the starting address location specified by the previously referenced CCS word (i.e., location 272). When execution of the add operation proceeds to a particular point, as seen from FIG. 10d, the processor 700 reads out a microinstruction word which includes a PIPE code specifying a type 4 start.

Upon the decoding of the PIPE code, the decoder circuits 704-114 generate signals which force the hardware circuits of block 704-102 to control state FPOA at the end of a fourth cycle. This enables the processor 700 to begin its processing of the next two instructions (LDA) in a pipeline fashion. That is, under hardware control, processor 700 carries out the indicated I cycle and cache operations during cycles 5 and 6.

As seen from FIG. 10d, the processor 700 stops further I and C cycles of operation during the execution of the add operation under microprogram control until the generation of a type 5 release. During a last E cycle of the add execution operation, the processor 700 reads out a microinstruction word having a PIPE field coded to specify a type 5 release. The decoder circuits 704-114 generate signals in response to this code which enables the circuits of block 704-102 to release itself from its current control state and continue instruction processing in a pipeline fashion. As seen from FIG. 10d, the circuits of block 704-102 remain in control state FPOA to begin processing of a third LDA instruction (ninth cycle). Concurrent therewith, the cache unit 750 executes a cache cycle of operation and the processor 700, under microprogram control, performs an E cycle of operation completing the execution of the first LDA instruction.

As mentioned above, the processor 700 through the combined use of types 4 and 5 restarts is able to execute I and C cycles of operation concurrent with the completing of the E cycles of another instruction.

FIG. 10e illustrates the use of a type 6 restart in connection with an EDIT (MVE) instruction. This instruction has the format shown in FIG. 9b. It is assumed that the instruction is coded to specify that the first descriptor or operand is of an indirect length (i.e., the RL bit of FIG. 9c is a binary ONE). During control state FPOA, the circuits of block 704-110 are conditioned by the MF1 field stored in the RBIR gegister 704-152 to switch the control flag flip-flop FRL to a binary ONE. Also, the processor 700 generates a read single command to cache unit 750 to fetch the next word of the instruction (descriptor 1).

During a next cycle, the circuits of block 704-110 have switched to control state FPOP. Also, the cache unit 750 executes a cache cycle in response to the cache read single command. Since signal FRL is a binary ONE, the circuits of block 704-102 switch to control state FESC and set the indicator flip-flop FINDA (see FIG. 7).

During the third cycle, the processor 700 begins the execution of the MVE instruction under the control of the routine specified by the CCS address of the CCS word referenced by the MVE op-code (020,1). As seen from FIG. 8, during the execution of the MVE routine, the processor 700 performs a branch operation based upon testing of the state of the FINDA flip-flop. Since the flip-flop is set to a binary ONE, the ECS control store 701-2 branches to an indirect length routine. The processor 700, during the execution of this routine, generates the required address for fetching the indirect length descriptor.

As seen from FIG. 10e, a last microinstruction word in the routine read out from the ECS control store 701-2 (cycle 5) includes a PIPE field coded to specify a type 6 restart. This causes the decoder circuits 704-146 to generate signals which condition the circuits of block 704-102 to switch to control state FPOP (cycle 6) as shown in FIG. 10e. This enables the processor 700 to continue processing of the remaining operand descriptors under hardware control. It will be appreciated that a similar sequence of operations will be performed for each operand descriptor having an indirect length. In each case, the circuits of block 704-102 will be switched to control state FPOP in response to a type 6 restart enabling the processor 700 to continue the execution of the MVE instruction in a pipeline fashion. For further details regarding the manner in which processor 700 executes an MVE instruction, reference may be made to the referenced related patent applications.

From the foregoing, it is seen how the arrangement of the preferred embodiment of the present invention permits additional flexibility in switching control so as to provide efficient pipeline processing of instructions.

    ______________________________________                                          APPENDIX A                                                                    ______________________________________                                         SINGLE WORD INSTRUCTIONS                                                               DATA MOVEMENT                                                          LDA     Load A                                                                 LDQ     Load Q                                                                 LDAQ    Load AQ                                                                LDAC    Load A and Clear                                                       LDQC    Load Q and Clear                                                       LDXn    Load Xn (n = 0, 1, ...7)                                               LXLn    Load Xn from Lower (n = 0, 1, ...7)                                    LCA     Load Complement A                                                      LREG    Load Registers                                                         LCQ     Load Complement Q                                                      LCAQ    Load Complement AQ                                                     LCXn    Load Complement Xn (n = 0, 1, ...7)                                    EAA     Effective Address to A                                                 EAQ     Effective Address to Q                                                 EAXn    Effective Address to Xn (n = 0, 1, ...7)                               LDI     Load Indicator Register                                                STA     Store A                                                                STQ     Store Q                                                                STAQ    Store AQ                                                               STXn    Store Xn into Upper (n = 0, 1, ...7)                                   SXLn    Store Xn into Lower (n = 0, 1, ...7)                                   SREG    Store Register                                                         STCA    Store Character of A (6 bit)                                           STCQ    Store Character of Q (6 bit)                                           STBA    Store Character of A (9 bit)                                           STBQ    Store Character of Q (9 bit)                                           STI     Store Indicator Register                                               STT     Store Timer Register                                                   SBAR    Store Base Address Register                                            STZ     Store Zero                                                             STCl    Store Instruction Counter plus 1                                       STC2    Store Instruction Counter plus 2                                       ARS     A Right Shift                                                          QRS     Q Right Shift                                                          LRS     Long Right Shift                                                       ALS     A Left Shift                                                           QLS     Q Left Shift                                                           LLS     Long Left Shift                                                        ARL     A Right Logic                                                          QRL     Q Right Logic                                                          LRL     Long Right Logic                                                       ARL     A Left Rotate                                                          QLR     Q Left Rotate                                                          LLR     Long Left Rotate                                                               FIXED POINT ARITHMETIC                                                 ADA     Add to A                                                               ADQ     Add to Q                                                               ADAQ    Add to AQ                                                              ADXn    Add to Xn (n = 0, 1, ...7)                                             ASA     Add Stored to A                                                        ASQ     Add Stored to Q                                                        ASXn    Add Stored to Xn (n = 0, 1, ...7)                                      ADLA    Add Logic to A                                                         ADLQ    Add Logic to Q                                                         ADLAQ   Add Logic to AQ                                                        ADLXn   Add Logic to Xn (n = 0, 1, ...7)                                       AWCA    Add With Carry to A                                                    AWCQ    Add With Carry to Q                                                    ADL     Add Low to AQ                                                          AOS     Add One to Storage                                                     SBA     Subtract from A                                                        SBQ     Subtract from Q                                                        SBAQ    Subtract from AQ                                                       SBXn    Subtract from Xn (n = 0, 1, ...7)                                      SSA     Subtract Stored from A                                                 SSQ     Subtract Stored from Q                                                 SSXn    Subtract Stored from Xn (N = 0, 1, ...7)                               SBLA    Subtract Logic from A                                                  SBLQ    Subtract Logic from Q                                                  SBLAQ   Subtract Logic from AQ                                                 SBLXn   Subtract Logic from Xn (n = 0, 1, ...7)                                SWCA    Subtract With Carry from A                                             SWCQ    Subtract With Carry from Q                                             MPY     Multiply Integer                                                       MPF     Multiply Fraction                                                      DIV     Divide Integer                                                         DVF     Divide Fraction                                                        NEG     Negate A                                                               NEGL    Negate Long                                                                    BOOLEAN OPERATIONS                                                     ANA     AND to A                                                               ANQ     AND to Q                                                               ANAQ    AND to AQ                                                              ANXn    AND to Xn (n = 0, 1, ...7)                                             ANSA    AND to Storage A                                                       ANSQ    AND to Storage Q                                                       ANSXn   AND to Storage Xn (n = 0, 1, ...7)                                     ORA     OR to A                                                                ORQ     OR to Q                                                                ORAQ    OR to AQ                                                               ORXn    OR to Xn (n = 0, 1, ...7)                                              ORSA    OR to Storage A                                                        ORSQ    OR to Storage Q                                                        ORSXn   OR to Storage Xn (n = 0, 1, ...7)                                      ERA     Exclusive OR to A                                                      ERQ     Exclusive OR to Q                                                      ERAQ    Exclusive OR to AQ                                                     ERXn    Exclusive OR to Xn (n = 0, 1, ...7)                                    ERSA    Exclusive OR to Storage A                                              ERSQ    Exclusive OR to Storage Q                                              ERSXn   Exclusive OR to Storage Xn (n = 0, 1, ...7)                                    COMPARE                                                                CMPA    Compare With A                                                         CMPQ    Compare With Q                                                         CMPAQ   Compare With AQ                                                        CMPXn   Compare With Xn (n = 0, 1, ...7)                                       CWL     Compare With Limits                                                    CMG     Compare With Magnitude                                                 CMK     Compare Masked                                                         SZN     Set Zero Negative Indicators from Memory                               SZNC    Set Zero Negative Indicator from Storage and                                   Clear                                                                  CANA    Comparative AND With A                                                 CANQ    Comparative AND With Q                                                 CANAQ   Comparative AND With AQ                                                CANXn   Comparative AND With Xn (n = 0, 1, ...7)                               CNAA    Comparative NOT With A                                                 CNAQ    Comparative NOT With Q                                                 CNAAQ   Comparative NOT With AQ                                                CNAXn   Comparative NOT With Xn (n = 0, 1, ...7)                                       FLOATING POINT                                                         FLD     Floating Load                                                          DFLD    Double Precision Floating Load                                         LDE     Load Exponent Register                                                 FST     Floating Store                                                         DFST    Double Precision Floating Store                                        STE     Store Exponent Register                                                FSTR    Floating Store Rounded                                                 DFSTR   Double Precision Floating Store Rounded                                FAD     Floating Add                                                           UFA     Unnormalized Floating Add                                              DFAD    Double Precision Floating Add                                          DUFA    Double Precision Unnormalized Floating Add                             ADE     Add to Exponent Register                                               FSB     Floating Subtract                                                      UFS     Unnormalized Floating Subtract                                         DFSB    Double Precision Floating Subtract                                     DUFS    Double Precision Unnormalized Floating Subtract                        FMP     Floating Multiply                                                      UFM     Unnormalized Floating Multiply                                         DFMP    Double Precision Floating Multiply                                     DUFM    Double Precision Unnormalized Floating Multiply                        FDV     Floating Divide                                                        FDI     Floating Divide Inverted                                               DFDV    Double Precision Floating Divide                                       DFDI    Double Precision Floating Divide Inverted                              FNEG    Floating Negate                                                        FNO     Floating Normalize                                                     FRD     Floating Round                                                         DFRD    Double Precision Floating Round                                        FCMP    Floating Compare                                                       FCMG    Floating Compare Magnitude                                             DFCMP   Double Precision Floating Compare                                      DFCMG   Double Precision Floating Compare Magnitude                            FSZN    Floating Set Zero and Negative Indicators from                                 Memory                                                                         TRANSFER OF CONTROL                                                    TRA     Transfer Unconditionally                                               TSXn    Transfer and Set Index Register                                        TSS     Transfer and Set Slave                                                 RET     Return                                                                 TZE     Transfer on Zero                                                       TNZ     Transfer on Not Zero                                                   TMI     Transfer on Minus                                                      TPL     Transfer on Plus                                                       TRC     Transfer on Carry                                                      TNC     Transfer On No Carry                                                   TOV     Transfer on Overflow                                                   TEO     Transfer on Exponent Overflow                                          TEU     Transfer on Exponent Underflow                                         TTF     Transfer on Tally Runout Indicator OFF                                 TTN     Transfer on Tally Runout Indicator ON                                  TPNZ    Transfer on Plus and Nonzero                                           TMOZ    Transfer on Minus or Zero                                              TRTN    Transfer on Truncation Indicator ON                                    TRTF    Transfer on Truncation Indicator OFF                                           MISCELLANEOUS                                                          NOP     No Operation                                                           BCD     Binary To Binary-Coded-Decimal                                         GTB     Gray to Binary                                                         XEC     Execute                                                                XED     Execute Double                                                         MME     Master Mode Entry                                                      DRL     Derail                                                                 RPT     Repeat                                                                 RPD     Repeat Double                                                          RPL     Repeat Link                                                            RCCL    Read Calendar Clock                                                    SPL     Store Pointers and Lengths                                             LPL     Load Pointers and Lengths                                                      ADDRESS REGISTER                                                       LARn    Load Address Register n                                                LAREG   Load Address Registers                                                 SARn    Store Address Register n                                               SAREG   Store Address Registers                                                AWD     Add Word Displacement to Specified AR                                  A9BD    Add 9-bit Character Displacement To Specified                                  AR                                                                     A6BD    Add 6-bit Character Displacement To Specified                                  AR                                                                     A4BD    Add 4-bit Character Displacement To Specified                                  AR                                                                     ABD     Add Bit Displacement to Specified AR                                   SWD     Subtract Word Displacement from Specified AR                           S9BD    Subtract 9-bit Character Displacement from                                     Specified AR                                                           S6BD    Subtract 6-bit Character Displacement from                                     Specified AR                                                           S4BD    Subtract 4-bit Character Displacement from                                     Specified AR                                                           SBD     Subtract Bit Displacement from Specified AR                            AARn    Alphanumeric Descriptor to ARn                                         NARn    Numeric Descriptor to ARn                                              ARAn    ARn to Alphanumeric Descriptor                                         ARNn    ARn to Numeric Descriptor                                                      MASTER MODE                                                            DIS     Delay Until Interrupt                                                  LBAR    Load Base Address Register                                             LDT     Load Timer Register                                                    LLUF    Load Lockup Fault Register                                             SCPR    Replaced with SFR                                                      SFR     Store Fault Register                                                   LCCL    Load Calendar Clock                                                    RIMR    Read Interrupt Mask Register                                           LIMR    Load Interrupt Mask Register                                           RRES    Read Reserved Memory                                                   CIOC    Connect I/O Channel                                                            EXTENDED MEMORY                                                        LBER    Load Base Extension Register                                           LMBA    Load Master Bar A                                                      LMBB    Load Master Bar B                                                      SBER    Store Base Extension Register                                          SMBA    Store Master Bar A                                                     SMBB    Store Master Bar B                                                     MLDA    Master Load A                                                          MLDQ    Master Load Q                                                          MLDAQ   Master Load AQ                                                         MSTA    Master Store A                                                         MSTQ    Master Store Q                                                         MSTAQ   Master Store AQ                                                        RPN     Read Processor Number                                                  HALT    Halt                                                                   MULTIWORD INSTRUCTIONS                                                                 ALPHANUMERIC                                                           MLR     Move Alphanumeric Left to Right                                        MRL     Move Alphanumeric Right to Left                                        MVT     Move Alphanumeric With Translation                                     CMPC    Compare Alphanumeric Character String                                  SCD     Scan Character Double                                                  SCDR    Scan Character Double in Reverse                                       TCT     Test Character and Translate                                           TCTR    Test Character and Translate in Reserve                                SCM     Scan With Mask                                                         SCMR    Scan With Mask in Reserve                                                      NUMERIC                                                                MVN     Nove Numeric                                                           CMPN    Compare Numeric                                                        AD3D    Add Using three Decimal Operands                                       AD2D    Add Using two Decimal Operands                                         SB3D    Subtract Using 3 Decimal Operands                                      SB2D    Subtract Using 2 Decimal Operands                                      MP3D    Multiply Using 3 Decimal Operands                                      MP2D    Multiply Using 2 Decimal Operands                                      DV3D    Divide Using 3 Decimal Operands                                        DV2D    Divide Using 2 Decimal Operands                                                BIT STRING                                                             CSL     Combine Bit Strings Left                                               CSR     Combine Bit Strings Right                                              SZTL    Set Zero and Truncation Indicator with Bit                                     Strings Left                                                           SZTR    Set Zero and Truncation Indicator with Bit                                     Strings Right                                                          CMPB    Compare Bit Strings                                                            CONVERSION                                                             DTB     Decimal to Binary Convert                                              BTD     Binary to Decimal Convert                                                      EDIT MOVE                                                              MVE     Move Alphanumeric Edited                                               MVNE    Move Numeric Edited                                                            MULTIWORD                                                              CMPCT   Compare Characters and Translate                                       MTR     Move to Register                                                       MTM     Move to Memory                                                         MVNX    Move Numeric Extended                                                  CMPNX   Compare Numeric Extended                                               AD3DX   Add Using three Decimal Operands Extended                              AD2DX   Add Using two Decimal Operands Extended                                SB3DX   Subtract Using 3 Decimal Operands Extended                             SB2DX   Subtract Using 2 Decimal Operands Extended                             MP3DX   Multiply Using 3 Decimal Operands Extended                             MP2DX   Multiply Using 2 Decimal Operands Extended                             DV3DX   Divide Using 3 Decimal Operands Extended                               DV2DX   Divide Using 2 Decimal Operands Extended                               MVNEX   Move Numeric Edited Extended                                                   VIRTUAL MEMORY MANAGEMENT                                                      PRIVILEGED INSTRUCTIONS                                                LDWS    Load Working Space Registers                                           STWS    Store Working Space Registers                                          LDSS    Load Safe Store Register                                               STSS    Store Safe Store Register                                              LDAS    Load Argument Stack Register                                           LDPS    Load Parameter Stack Register                                          LPDBR   Load Page Table Directory Base Register                                SPDBR   Store Page Table Directory Base Register                               LDDSD   Load Data Stack Descriptor Register                                    STDSD   Store Data Stack Descriptor Register                                   LDDSA   Load Data Stack Address Register                                       STDSA   Store Data Stack Address Register                                      CAMP    Clear Associative Memory Paged                                         CCAC    Clear Cache                                                            EPAT    Effective Address and Pointer to Test                                          ALL MODE INSTRUCTIONS                                                  LDO/    Load Option Register                                                   STO/    Store Option Register                                                  STPS    Store Parameter Stack Register                                         STAS    Store Argument Stack Register                                          PAS     POP Argument Stack                                                     LDDn    Load Descriptor (Register) n                                           SDRn    Store Descriptor Register n                                            STPn    Store Pointer n                                                        LDPn    Load Pointer (Register) n                                              STDn    Store Descriptor Register n                                            EPPRn   Effective Pointer to Pointer (Register) n                              LDEAn   Load Extended Address n                                                CLIMB   Domain Transfer                                                        ______________________________________                                    

It will be appreciated that many modifications may be made to the preferred embodiment of the present invention without departing from its teachings.

While in accordance with the provisions and statutes there has been illustrated and described the best form of the invention known, certain changes may be made to the system described without departing from the spirit of the invention as set forth in the appended claims and, in some cases, certain features of the invention may be used to advantage without a corresponding use of other features. 

What is claimed is:
 1. A data processing system including a microprogrammable data processing unit for performing data manipulations under the control of instructions wherein the processing of instructions proceed in a pipelined fashion wherein each instruction is processed in a number of different phases of operation to completion, said data processing unit comprising:a plurality of registers for storing instructions to be processed, each instruction including a multibit operation code; a first addressable control store coupled to a first one of said plurality of registers for receiving signals corresponding to said multibit operation code of an instruction to be processed, said first control store including a plurality of locations, each for storing a word including at least a multibit control sequence code having less bits than said operation code and an address, said control sequence code specifying one of a number of hardwired control sequences and said address identifying a first microinstruction of a different one of a plurality of execution sequences; a cycled addressable second control store including a plurality of locations for storing at least one microinstruction of a different one of said plurality of execution sequences; an address register connected to receive said address from said first control store and connected to said second control store for read out of the microinstruction contents of a location during a cycle of operation; an output register connected to said second control store for temporarily storing said microinstruction contents read out during said cycle of operation; hardwired control state sequencing means coupled to said first control store including sequence decoder circuit means for decoding said control sequence codes, said hardwired control sequencing means for generating different sequences of control signals for defining the different operations to be performed during a first one of said phases of operation for each instruction, said hardwired control sequencing means, being conditioned by each control sequence code within a certain class read out in response to the operation code of an instruction being processed, for generating a predetermined one of said different sequences of control signals, for performing said operations during said first one of said phases of said instruction, for transferring said address into said address register, for continued processing of said instruction under the control of the specified one of said plurality of execution sequences, and for placing said sequencing means in a predetermined state, said specified execution sequence including a microinstruction containing a restart code bit pattern; and, decoder circuit means coupled to said hardwired control state sequencing means and to said output register, said decoder circuit means being operative upon the read out of said microinstruction restart code pattern from said second control store into said output register to generate signals for switching said hardwired control state sequencing means from said predetermined state to another state to continue instruction processing in said pipelined fashion.
 2. The system of claim 1 wherein said hardwired sequence control means includes:a plurality of bistable elements coupled to said sequence decoder circuit means, said plurality of bistable elements being conditioned by said sequence decoder circuit means to switch states for generating said different sequences of control signals and said decoder circuit means in response to said each control sequence code switching a predetermined one of said plurality of bistable elements to a binary ONE corresponding to an escape state.
 3. The system of claim 1 wherein said restart code contains a first coded bit pattern, said decoder circuit means being conditioned by said first coded bit pattern to generate signals for switching said hardwired control state sequencing means from said predetermined state to one of a plurality of states for loading the next instruction to be processed into said first one of said registers.
 4. The system of claim 3 wherein said one of said plurality of states is selected in accordance with the coding of said sequence control code and status signals corresponding to certain conditions.
 5. The system of claim 4 wherein said system further includes buffer storage apparatus coupled to said processing unit for providing fast access to instructions and data stored therein, first, second, third and fourth ones of said bistable elements designated FXRPT, FPI-INIT, FPIM-1 and FPOA respectively being coupled to receive signals corresponding to said first coded bit pattern representative of a type 1 restart, said first, second, third and fourth bistable elements being conditioned to switch to a binary ONE in accordance with the following expressions:

    FXRPT=XED+RPTS;

    fpi-init=xed+rpts·str-cpr;

    fpim-1=xed+rpts·str-cpr·ibuf-emty; and,

    FPOA=XED+RPT·STR-CPR·IBUF-EMTY

wherein the terms XED and RPTS designate that the instruction being processed is an execute double or repeat respectively as indicated by said control sequence code while the terms STR-CPR and IBUF-EMTY designate the presence of a store compare condition and buffer empty condition respectively indicated by said status signals.
 6. The system of claim 4 wherein said microinstruction containing said restart code bit pattern is included within a predetermined point within said specified execution sequence so as to provide no breaks within said number of different phases of operation.
 7. The system of claim 6 wherein said instruction includes at least one address, said system further including buffer storage apparatus coupled to said processing unit for providing fast access to instructions and data stored therein and said different phases of operation including an instruction cycle (I cycle) wherein an instruction operand address is generated, a cache cycle(C cycle) wherein said buffer storage apparatus fetches an operand specified by said instruction operand address and an execution cycle (E cycle) wherein the manipulations specified by the instruction operation code to be performed upon said operand are executed by said data processing unit, said predetermined point within said specified execution sequence occurring at a time which corresponds to two cycles prior to the completion of the execution of said instruction during said E cycle.
 8. The system of claim 1 wherein said system further includes buffer storage apparatus coupled to said processing unit for providing fast access to data and instructions stored therein, said restart code containing a second coded bit pattern, said decoder circuit means being conditioned by said second coded bit pattern to generate signals for switching said hardwired control state sequencing means from said predetermined state corresponding to an escape state to said another state corresponding to a first of a number of states, said hardwired control state sequencing means including means for generating signals during said number of states for conditioning said buffer storage apparatus to fetch blocks of instructions automatically under hardwired control to enable said processing unit to begin processing of a new block of instructions.
 9. The system of claim 1 wherein said restart code contains a third coded bit pattern, said decoder circuit means being conditioned by said third bit pattern to generate signals for switching said hardwired control state sequencing means from said predetermined state corresponding to an escape state to said another state corresponding to an initial state, said hardwired sequencing means generating other predetermined ones of said different sequences of control signals in accordance with the codings of other control sequence codes read out from said first control store in response to the operation codes of successive instructions as stored in said first one of said plurality of registers for performing operations during certain ones of said phases in parallel with the read out of microinstructions from said second control store.
 10. The system of claim 9 wherein said specified execution sequence includes a last microinstruction containing another restart code bit pattern, said hardwired sequencing means stopping the generating of further sequences of control signals after a predetermined time interval, said second control store continuing the successive read out of microinstructions including said last microinstruction of said specified execution sequence into said output register andsaid decoder circuit means being conditioned by said another restart code bit pattern to generate signals for releasing said hardwired sequencing means from a last current state to a next state for continuing the processing of further instructions.
 11. A data processing system including a microprogrammable data processing unit for performing data manipulations under the control of instructions wherein the processing of instructions proceed in a pipelined fashion wherein each instruction is processed in a number of different phases of operation to completion, said data processing unit comprising:a plurality of registers for storing instructions to be processed, each instruction including a multibit operation code at least one address and a tag field coded for specifying the type address modification to be performed upon said address; a first addressable control store coupled to a first one of said plurality of registers for receiving signals corresponding to said multibit operation code of an instruction to be processed, said first control store including a plurality of locations, each for storing a word including at least a multibit control sequence code having less bits than said operation code and an address, said control sequence code specifying one of a number of hardwired control sequences and said address identifying a first microinstruction of a different one of a plurality of execution sequences; a cycled addressable second control store including a plurality of locations for storing at least one microinstruction of a different one of said plurality of execution sequences and microinstructions of a number of address modification routines; an address register connected to receive said address from said first control store and connected to said second control store for read out of the microinstruction contents of a location during a cycle of operation; an output register connected to said second control store for temporarily storing said microinstruction contents read out during said cycle of operation; control flag indicator circuit means coupled to said first one of said plurality of registers, and to said second control store, said control flag indicator circuit means in response to a predetermined coding of said tag field to generate an output control signal indicative of a predetermined type of address modification; hardwired control state sequencing means coupled to said first control store and to said control flag indicator circuit means, including sequence decoder circuit means for decoding said control sequence codes, said hardwired control sequencing means for generating different sequences of control signals for defining the different operations to be performed during a first one of said phase of operation for each instruction, said hardwired control sequencing means, being conditioned by each control sequence code within a certain class read out in response to the operation code of an instruction being processed and being further conditioned by said control signal, for generating a predetermined one of said different sequences of control signals resulting in said sequencing means being switched to a state, for performing of an address development operation under microprogram control, and for transferring control to one of said address modification routines for generation of an effective address, said one address modification routine including a last microinstruction containing a restart code bit pattern; and, decoder circuit means coupled to said hardwired control state sequencing means and to said output register, said decoder circuit means being operative upon the read out of said microinstruction restart code pattern from said second control store into said output register to generate signals for switching said hardwired control state sequencing means from said predetermined state to another state to continue the processing of said instruction in said pipelined fashion.
 12. The system of claim 11 wherein said restart code contains a fourth coded bit pattern, said decoder circuit means being conditioned by said second coded bit pattern to generate signals for switching said hardwired control state sequencing means from said predetermined state to an initial control state, said hardwired control sequencing means being operative to generate a predetermined one of said different sequences of control signals for completing the operations of first and second phases and for transferring control to one of said plurality of execution sequences specified by the address read out in response to said instruction operation code for completion of a third phase of operation.
 13. A data processing system including a microprogrammable data processing unit for performing data manipulations under the control of instructions wherein the processing of instructions proceed in a pipelined fashion wherein each instruction is processed in a number of different phases of operation to completion, said data processing unit comprising:a plurality of registers for storing instructions to be processed, certain ones of said instructions corresponding to multiword instructions, each including a multibit operation code, a plurality of addresses and a corresponding number of operand modification fields, at least one of said operand modification fields being coded to specify that the operand associated therewith is of a predetermined characteristic; a first addressable control store coupled to a first one of said plurality of registers for receiving signals corresponding to said multibit operation code of an instruction to be processed, said first control store including a plurality of locations, each for storing a word including at least a multibit control sequence code having less bits than said operation code and an address, said control sequence code specifying one of a number of hardwired control sequences and said address identifying a first microinstruction of a different one of a plurality of execution sequences; a cycled addressable second control store including a plurality of locations for storing at least one microinstruction of a different one of said plurality of execution sequences and microinstructions of a number of operand address processing routines; an address register connected to receive said address from said first control store and connected to said second control store for read out of the microinstruction contents of a location during a cycle of operation; an output register connected to said second control store for temporarily storing said microinstruction contents read out during said cycle of operation; control flag indicator circuit means coupled to said first one of said plurality of registers, and to said second control store, said control flag indicator circuit means in response to a predetermined coding of said tag field to generate an output control signal indicative of a predetermined type of address modification; hardwired control state sequencing means coupled to said first control store and to said control flag indicator circuit means including sequence decoder circuit means for decoding said control sequence codes, said hardwired control sequencing means for generating different sequences of control signals for defining the different operations to be performed during a first one of said phase of operation for each instruction, said hardwired control sequencing means, being conditioned by each control sequence code within a certain class read out in response to the operation code of an instruction being processed and being further conditioned by said control signal, for generating a predetermined one of said different sequences of control signals, for transferring said address into said address register, for continued processing of said instruction under the control of a specified one of said plurality of execution sequences, and for placing said sequencing means in a predetermined state, said specified execution sequence including as a first microinstruction one coded to test the states of signals generated by said control flag indicator circuit means, said second control store being conditioned by said first microinstruction to branch to one of said operand address processing routines, said one operand address processing routine including a last microinstruction containing a restart code bit pattern; and, decoder circuit means coupled to said hardwired control state sequencing means and to said output register, said decoder circuit means being operative upon the read out of said microinstruction restart code pattern from said second control store into said output register to generate signals for switching said hardwired control state sequencing means from said predetermined state to another state within said predetermined sequence of control signals to continue the processing of said multiword instruction in said pipelined fashion.
 14. The system of claim 13 wherein said hardwired control state sequencing means is conditioned to generate control signals for completing said predetermined sequence so as to continue the processing of the remaining ones of said plurality of addresses under hardwired control.
 15. The system of claim 14 wherein said hardwired sequence control means includes:a plurality of bistable elements coupled to said sequence decoder circuit means, said plurality of bistable elements being conditioned by said sequence decoder circuit means to switch states for generating said different sequences of control signals and said decoder circuit means in response to said each control sequence code of said predetermined class switching a predetermined one of said plurality of bistable elements to a binary ONE corresponding to an escape state.
 16. The system of claim 15 wherein said restart code contains a fifth coded bit pattern, said decoder circuit means being conditioned by said first coded bit pattern to generate signals for switching said hardwired control state sequencing means from said predetermined state to one of a plurality of states for continuing the processing of said multiword instruction.
 17. The system of claim 16 wherein said one of said plurality of states is selected in accordance with the coding of said sequence control code.
 18. The system of claim 17 wherein said system further includes buffer storage apparatus coupled to said processing unit for providing fast access to instructions and data stored therein and said different phases of operation including an instruction cycle (I cycle) wherein one of said instruction operand addresses is generated, a cache cycle (C cycle) wherein said buffer storage apparatus fetches an operand specified by said one instruction operand address and an execution cycle (E cycle) wherein the manipulations specified by the instruction operation code to be performed upon said instruction operands are executed by said data processing unit.
 19. A data processing system comprising:an addressable main store having a plurality of word locations for storing information including data and instructions; a cache unit coupled to said main store for providing immediate access to data and instructions fetched from said main store, said cache unit having a plurality of addressable locations and including control means for fetching information from said main store; and, a microprogrammable data processing unit coupled to said cache unit, said microprogrammable data processing unit for performing data manipulations under the control of instructions wherein the processing of instructions proceed in a pipelined fashion wherein each instruction is processed in a number of different phases of operation to completion, said data processing unit comprising: a plurality of registers for storing instructions to be processed, each instruction including a multibit operation code; a first addressable control store coupled to a first one of said plurality of registers for receiving signals corresponding to said multibit operation code of an instruction to be processed, said first control store including a plurality of locations, each for storing a word including at least a multibit control sequence code having less bits than said operation code and an address, said control sequence code specifying one of a number of hardwired control sequences and said address identifying a first microinstruction of a different one of a plurality of execution sequences; a cycled addressable second control store including a plurality of locations for storing at least one microinstruction of a different one of said plurality of execution sequences and microinstructions of a number of operand address processing routines; an address register connected to receive said address from said first control store and connected to said second control store for read out of the microinstruction contents of a location during a cycle of operation; an output register connected to said second control store for temporarily storing said microinstruction contents read out during said cycle of operation; hardwired control state sequencing means coupled to said first control store, said hardwired control sequencing means for generating different sequences of control signals for defining the different operations to be performed during first and second ones of said phases of operation for each instruction, said hardwired control sequencing means including:sequence decoder circuit means coupled to said first control store for decoding said control sequence codes; a plurality of bistable elements coupled to said sequence decoder circuit means, said plurality of bistable elements being conditioned by said sequence decoder circuit means to switch states for generating said different sequences of control signals, and said decoder circuit means in response to said each control sequence code within a certain class for switching a predetermined one of said plurality of bistable elements to a binary ONE state and transferring said address into said address register for continued processing of said instruction under the control of a specified one of said plurality of execution sequences, said specified execution sequence including a microinstruction containing a restart code bit pattern; and, decoder circuit means coupled to said hardwired control state sequencing means and to said output register, said decoder circuit means being operative upon the read out of said microinstruction restart code pattern from said second control store into said output register to generate signals for switching said predetermined one of said plurality of bistable elements to a binary ZERO state and another one of said bistable elements to said binary ONE state to continue the processing of said instruction.
 20. The system of claim 19 wherein said restart code contains a first coded bit pattern, said decoder circuit means being conditioned by said first coded bit pattern to generate signals for switching said another one of said bistable elements to said binary ONE state for loading the next instruction to be processed into said first one of said registers.
 21. The system of claim 20 wherein said one of said another one of said plurality of bistable elements is selected in accordance with the coding of said sequence control code and status signals corresponding to certain conditions.
 22. The system of claim 21 wherein first, second, third and fourth ones of said bistable elements designated FXRPT, FPI-INIT, FPIM-1 and FPOA respectively being coupled to receive signals corresponding to said first coded bit pattern representative of a type 1 restart, said first, second, third and fourth bistable elements being conditioned to switch to a binary ONE in accordance with the following expressions:

    FXRPT=XED+RPTS;

    fpi-init=xed+rpts·str-cpr;

    fpim-1=xed+rpts·str-cpr·ibuf-emty; and,

    FPOA=XED+RPT·STR-CPR·IBUF-EMTY

wherein the terms XED and RPTS designate that the instruction being processed is an execute double or repeat respectively as indicated by said control sequence code while the terms STR-CPR and IBUF-EMPTY designate the presence of a store compare condition and buffer empty condition respectively indicated by said status signals.
 23. The system of claim 22 wherein said mircoinstruction containing said restart code bit pattern is included within a predetermined point within said specified execution sequence so as to provide no breaks within said number of different phases of operation.
 24. The system of claim 23 wherein each instruction includes at least one address, said system further including buffer storage apparatus coupled to said processing unit for providing fast access to instructions and data stored therein and said different phases of operation including an instruction cycle (I cycle) wherein an instruction operand address is generated, a cache cycle (C cycle) wherein said buffer storage apparatus fetches an operand specified by said instruction operand address and an execution cycle (E cycle) wherein the manipulations specified by the instruction operation code to be performed upon said operand are executed by said data processing unit, said predetermined point within said specified execution sequence occurring at a time which corresponds to two cycles prior to the completion of the execution of said instruction during said E cycle.
 25. The system of claim 19 wherein said restart code contains a third coded bit pattern, said decoder circuit means being conditioned by said third bit pattern to generate signals for switching said one of said plurality of bistable elements from said binary ONE state corresponding to an escape state to a binary ZERO state and another one of said bistable elements to a binary ONE state corresponding to an initial state, said plurality of bistable elements generating another predetermined one of said different sequences of control signals in accordance with the coding of a next control sequence code read out from said first control store in response to the operation code of a next instruction stored in said first one of said plurality of registers for performing operations during certain ones of said phases in parallel with the read out of microinstructions from said second control store.
 26. The system of claim 25 wherein said specified execution sequence includes a last microinstruction containing another restart code including a fourth bit pattern, said plurality of bistable elements being inhibited from further switching after a predetermined time interval, said second control store continuing the successive read out of microinstructions including said last microinstruction of said specified execution sequence into said output register andsaid decoder circuit means being conditioned by said another restart code bit pattern to generate a release signal for enabling said plurality of bistable elements for switching, said another bistable element switching to a binary ZERO state while a different one of said plurality of bistable elements switches to a binary ONE state for continuing the processing of further instructions. 